in this video we're going to practice using the distance formula when the lines have not been given to us they've only given us the points it's even easier like this so all you do so for number one we want to find the distance of a b so you choose let's say you just choose a or b as your point number two so i'm just going to do it like that it really doesn't matter i promise you no matter which way you do it you will get the same answer so now we just use this formula remember this is the distance formula which is actually doing pythagoras okay many people don't know that it's actually just doing pythagoras i know i've mentioned that a lot but it just fascinates me that that formula is doing pythagoras for us okay but many people think that it's just a brand new formula but actually no so so let's go fill in the formula so it says that there's a square root and then we can do this like this and then i'm going to fill in everything that should be there so there's a minus there's a minus over there and then it says i must take the x value of point number two so point number two is a now which of them is the x value is it the minus two or the four well the x is always the first one so that's always going to be the minus 2 just like x is first in the alphabet so that's going to be a minus 2. then it says i must use the x value of point number one so i'll go to point number one which is this one now is the x value the minus one or is it the nine it's the minus one okay then the formula says i'm gonna use the y value of point number two so point number two is a so that's gonna be the four so i put a four over there and then the y value of point number 1 is 9. you see you literally just go plug everything in then what you do is you use your calculator at this point and you type it in exactly as you see it and the calculator will take care of all of the pluses and minuses and things like that and that's going to give you the square root of 26 but this question has asked us to do this to two decimal places and so that's going to give us 5.1 if you round up unfortunately we can only get one decimal place with that one because when you round up 5.099 it rounds to 5.1 moving on to number two which is the length of cd this time i'm going to make this point 2 just to change it up a bit but it doesn't actually change anything then gonna use the formula and fill in whatever i can so long with the two minuses and the two minuses so the first part is the x value of point number two so that's going to be that one over there oh no that's not right x value of point number two is this one because now this is our we said that d is our point number two so that's going to be a minus three then the formula says i'm gonna take the x value of point number one which is the two over there so i fill in the two then it's the y value of point number two which is the four and then it's the y value of point number one which is a7 then you go type all of this on the calculator and that's going to give you to 2 decimal places that's going to give you 5.83 so i trust that by now you are fully comfortable with using the distance formula