hello our most developed student my name is confident and welcome to the revision session for grade 9 and this is for you guys who are preparing for your term too and this lesson is meant to take you through uh some of the topics here so I'm going to have a follow-up videos where I'll be teaching you all the topics you need to know for your term too so in term two um these are the following topics that I expect you to be doing which is algebraic expressions algebraic equations as well as functions and relationships all right so if you want to get a distinction for your final exam these is the lessons that you must follow up now to make things easier for you ensure that you subscribe turn on that subscription button make sure that you turn it on and then every video that is going to come you will be notified this will help you to prepare for your final exam all right so let's skip this lesson studied algebraic expressions and then says understanding the basics let me bring some Basics to you so that you can know what to know look at this he says there are three main parts of an algebraic expression we are talking about the variable the coefficient as well as the constant tab now to demonstrate the three parts of an algebra let me give you an example for example let's say I've got here 3x squared minus 4X is a plus 2. and in this case I just want to show you now which one is the variable now when I talk about the variable the variable is the X the letters so that is your variable so the letter represent the what the variable all right and then what about the core efficient if we want to get the coefficient it is the number before the variable for example look at this number here you see that three so here we say 3 is the coefficient of x squared so this is the core efficient all right and then another coefficient that you can identify yes you are right it is this coefficient minus four so here minus 4 is the coefficient but is the coefficient of what is the coefficient of x you see but 3 is the coefficient of x squared so the number before the variable if it's an X you put X if there is a square as you can see is the coefficient of x squared and then we have got the constant term that is the number that does not contain the variable and in this case you see this plus 2 it does not have the letter so we call that the constant term all right so these are the three parts when you're talking about three parts of a variable now just quickly to recap on this again when you're talking about three parts of a variable I can give you another example to say negative 4 x to the power of three and then I say plus five and then from here I will say which one is your variable sometimes let me not say x here let me use a different one let me say a cubed for a cubed in this case a is the what a is the variable so that's your variable variable meaning it changes value it can take any value a can be 5 can be two can be any value so the letter is the variable and then look at this the coefficient now be careful here when I'm talking about the coefficient is the number that is attached to the variable or to the letter in this case look at this B is 4 but it's not only four it's four with the sign so that negative four it's minus four is the core efficient but is the coefficient of what of a cube I think that and then 5 which is positive in this case plus 5 is the now is the is the one without the letter we call that the word constant term icing that that's the constant all right so I think there is an example here that demonstrates that well look at it says consider the expression there is the expression that they've given in this is how many terms are in this expression so this is kind of a quick revision from grade 8 how many times look at this this is the first one this is the second one you just count them third and four so there are four terms here so how many terms here one two three four which is equal to four terms I sing that and then what is the constant term now constant means it does not have the letter in this case do you see it there is minus seven it doesn't have a what it doesn't have a variable or it doesn't have a letter and then the next one says State the core efficient of the term in x squared so let's identify determine x squared so x squared has got two x squared but they want the coefficient now I said the coefficient is the number before look at the number before it's two so here for x squared the question is what is 2. what about uh the coefficient for the term in y squared let's go and identify uh y squared there it is but now be careful with Y squared there is 9 and there is minus nine so now for y it's very important for you to recognize that it's minus the negative belong to 9 so it's minus what 9 y squared so the core efficient is 9 and the sine of 9 which is equal to what minus nine are you with me that is very very important and then here they're saying State the coefficient of the term in X now pay attention I want to show you something with x x is written uh with what uh it contains negative 18 x y now we want the coefficient of this and then we said the variable is the letter now we are confusing here because there is the letter X and the letter Y but now since I'm focusing on X this is my focus anything that is not X is the coefficient so in this case if I take out X here you see whatever I remain with is the coefficient so what is the coefficient the coefficient there is minus 18 y are you saying that that's how you can sometimes simple do that is the same way if I had wanted to do the same thing with uh for example or negative 9 y squared the first one when I say it negative 9y squared and they said State the coefficient of Y squared I can just remove y squared look what I'm remaining with with minus 9 is it and then the last one says State the coefficient of 1. now again I go back to the term where is y linked Y is linked to negative 18 x y so if I say negative 18 X Y but now remember my focus is y That's My so I need the coefficient of Y so what do I do I go to y i take out Y and there is the coefficient what is the coefficient is negative 18 x in this case X is no longer the one the variable because they say it I must focus on Y which is the variable so you just have to be careful when it comes to that all right and then lastly we are saying here determine the value of the expression if x is equal to 2 and Y is equal to minus 3. this is a very important part of substitution for example we are given 2 x squared minus 18 x y minus 7 and then here you are told X is equal to 2 and Y is equal to negative 3. now look at this with these values so it means where I see x what do I put I put 2 and when I say Y which is days y i put what I put minus 3 and then where there is X what do I put I put that so that's a they call it substitution so this is how you write it you're going to say 2 then where you see X you now do it like this you say x squared minus 18 when you see X put a bracket now and say X and you see why put a bracket and say y those are different variables minus seven then you can now interchange or substitute we call it substitution where there is X they told us what is X x is 2. see that so you put two bracket squared minus 18 remember X I put 2 and for y what do I put I put minus 3. and then minus 7 and then the calculator then at this stage it will give me the answer all right so you can then use your calculator as is don't do it in Parts but do it once so what you do you take a calculate I say two bracket and then you put two close the bracket squared as I say do it once minus 18 bracket 2 you open and close it open another one but now it's negative three it's better to use that negative not this one still the same but I prefer that one as a negative this is minus but the other one is negative three and then it's minus now it's minus seven but as I say you get the same answer which is 109 so 109 is the answer that you get all right so that is that guys as we are getting started with this lesson and I'm introducing the part of what as you see here I'm introducing the part of algebraic expressions now let's quickly look at these ones like and unlike terms now let's look at some examples of like terms if something is like for example two and two or two and four these are like because these are just numbers see they are like terms why they're just numbers what about if I do this 2X and 5X now look at it the main thing that makes something like if I say in like terms you look at the variable the letter so if the letter is x and the letter is x it means it's like terms for example to get a scenario of like terms let's say I've got um cows there are two two different guys I've got cows now let's say the word cows is that with the letter c say we have got five cows one guy has got five calves and another guy has got seven cows so you see that C is for cows so these are like terms we are all talking about cows but now let's say one uh let's use another animal dogs is d so let's say one has got five cows and the neighbor has got seven dogs now the question is are these like terms no we are dealing with cows and they're dealing with dogs hence we start saying these are unlike terms why C stands for cows d stands for dogs and these are different animals we are talking about so if I say 5C and 7D those are five cows in this case of the example I use and seven dogs there is nothing that is alike there is nothing that is similar so you can't do anything to this we are going to look at addition and subtraction of this all right I can go on and say if I say uh for example 3x squared look 3 x squared and I say 3x these are unlike terms they are unlike these guys why look at the square this is power two but if you don't see any power here it's power one it means they are different the fact that one has got a square and the other one does not have a square in as much as three is the same but these are different so they are called what unlike terms all right so sometimes they can give you something like this to say three x y like my X3 XY and let's say 5 y x so you ask yourself are these like terms the answer is yes this y x I can go on and write it as 5 start with x and then end with Y see now it's X Y X Y like terms right with me but if I do this again to see how sometimes they play around your mind if I say 2 x squared Y and 6 x y squared look at this one be careful now where does the power belong this squared comes or belongs to X and this squared in this case you see it belongs to Y these are unlike terms why because the other Square comes from X the other Square comes from y so these are unlike terms so just be careful whenever you're dealing with such things all right then that's why here it says addition and subtraction of like and unlike term says example understanding the negative sign importantly so let's look at this let's start with the first one above I say to you three cows I said one neighbor has got three cows another neighbor they say it's got six I mean eight cows C stands for cows all right so if I'm to add how many cows do I have altogether you just say three plus eight which is what you get eleven so now the total number there is 11 c meaning 11 cows don't forget the C C stands for cows that's how you add these things if I say I have got um a neighbor has got three cats C for cats and another neighbor has got two cats how many cats all together so you say three plus two which is five what five cats but now we can use the word c for kids which is five C similarly I can just say 3x you see plus 2X and then you're going to add you add three plus two what you get you get five five one five eggs avoid saying five x squared that is wrong why let's go back to our cats if I say three cats which is 3C plus two cats which is two c you don't say five cats squared you don't do that you don't say five cat squared something like that never exists it's just five cats that's why we call it 5c you don't have to multiply or put some exponents there are you with me now more examples if I say I have got for example 5 x y all right plus seven X Y so what you have to focus on are the variables is it X Y decide yes is this X Y decide yes which means they are the same like terms you see they are like they belong to the same group now I just focus on the numbers what am I supposed to do I'm supposed to add 5 plus 7 you can do that with the calculator it gives you 12 then the answer there is equal to 12 but what maintain your variable which was x y you don't have to do anything strange after that okay so let's look at another example here of like terms if I say you are given uh 8 x squared be careful now then minus 4 x squared be careful now doesn't matter you need to focus on the variable you ask yourself is it x squared on the other side yes is it x squared yes so it means they are like terms now it means you focus on the numbers so what are the numbers is eight but now there is no plus it's a minus so eight minus four that's what you do in the calculator you take a calculator and then you find out what is 8 minus four and the calculator will give you what we will give you a four then here you're going to say equal to so 8 minus four it's four then you maintain the variable which was 4 x squared is it making sense as I said you do not have to panic now there is another example if I say practical example I have got three curves and I've got five dogs and then I say ate these at the cows and the dogs so it will be three cows plus five dogs if I say add them together you can't tell me now that you're gonna add three plus five and then you ate you get eight eight what what I'm gonna have here is there an animal called cow dog you know cow dog have you ever seen such it doesn't exist meaning if I give you five cows plus I mean three cows plus five dogs you can't do anything to these they remain as three cows plus five dogs you can't do anything you can't add them remember this is a real reality you can't add something that is not related similarly if I say to you 3x plus 5y you can't do anything to this the x is different from y x can refer to different animal why you can refer to a different animal now you are eating them they need to make a strange animal in this case you understand X can refer to a different chemical why you can refer to a different chemical you can't add them together otherwise you create a bomb so this is X that is why the answer remains as 3x plus 5 for y you see that now just be careful whenever you're dealing with such but now look at this now if I say 2D which means two dogs a neighbor has got two dogs plus five cows that is one neighbor our neighbor the second neighbor has got three cows and he has got um let's say seven ducks now we want to add the animals together to say how many dogs are there how many cows are there so we're going to say here when you start adding two dogs plus five cows plus three cows and then one plus seven dogs now look at this obviously you can see that we are allowed to bring similar things together so I'm going to take this together so I'll say two dogs plus seven talks you see then in the center here I've got plus five cows plus three cups see that then equal to now I add the dogs together see d d means log two plus seven I've got nine dogs plus five plus three I've got eight cows then that's what I have when I'm adding them together I will say I've got nine dogs and eight cups don't need to do anything further because now if I add 9 and 8 I'm going to get 17 watt dog's cup you can't have that there is no animal called stocks cup so the answer here is nine talks and eight cows it's done Don't Force It nothing you can do addition and subtraction that's where it ends are you with me and then talks about the negative sign to be very sensitive of the negative side for example if I say 2X and then plus 5y and then I say minus 3x and then minus eight one is the something I told you about the dogs and the cows you bring things that are similar together for example when you rearrange look at this this is my Axis and this is my y's they need to be rearranged so that I bring them together so what will I have I'll have 2X see that minus 3x when I move it I move it with its sign so it is minus three so it goes with minus 3x then I've got that which is Plus 5y and then I've got that one with the sign is minus 8y all right then equal to your calculator will do the work look at this stuff first this is my X this is my X now remember we talked about the coefficient which is the number before x what are you seeing here I'm saying 2 and then the other one I'm not saying three what is it it's not three but it's minus three so you take a calculator and you say 2 minus three that's what you do 2 minus three what you get minus one that's what you write here to say my answer here is minus one but don't forget the variable the variable as X you see you do this something the other side you've got Y and Y once the variables are the same you focus on five minus eight that's what you do on the calculator So when you say 5 minus eight take a calculator right now and then you do 5 minus eight remember it's very important for you to practice so that you can see how it works five minus eight okay what negative three not just three but it's negative three okay let me maintain my pendant it's minus three but look at this minus three what was the variable it was y from here leave it like that you can't do anything between what x and you can't do anything between y are you with me so that is how you approach these are you with me so guys join me now in the next lesson whereby I'm going to continue with this part but now what are we going to focus on we're going to focus on division very important as well as the most important one very very important in the next lesson is multiplication I show you now how to multiply this and remember I told you if you are subscribed it's easier for you to see this lesson coming so all this will be what I start showing you and remember this is the foundation I'm laying a good foundation for you so that when we start attempting the previous papers you will see how easy it is to face that final exam I want you to get a distinction a good Mark so that even you know how your friends will be very envious of you your parents will just feel so proud of you that's what I want to give to you if this is what you want to achieve at the end of the year stick to this channel become a part of this Channel and I guarantee you you'll never go wrong we've come to the end of our first lesson thank you foreign [Music] [Applause] [Music]