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Current time:0:00Total duration:2:39

Calculating slope from tables

CCSS.Math:

Video transcript

we are asked what is the slope of the line that contains these points so pause this video and see if you can work through this on your own before we do it together all right now let's do it together and let's just remind ourselves what slope is slope is equal to change in Y this is the Greek letter Delta it looks like a triangle but it's shorthand for a change in Y over change in X sometimes you would see it written as y2 minus y1 over x2 minus x1 where you could kind of view x1 y1 is the starting point and why'd x2 y2 as the ending point so let's just pick two pair two XY pairs here and we can actually pick any two if we can assume that this is actually describing a line so we might as well just pick the first two so let's say that's our starting point and that's our finishing point so what is our change in X here so we're going from 2 to 3 so our change in X is equal to 3 minus 2 which is equal to 1 and you can see that to go from 2 to 3 just adding 1 and what's our change in Y our change in Y is our finishing Y 1 minus our starting Y 4 which is equal to negative 3 and you could have you didn't even have to do this math you would have been able to see to go from 2 to 3 you added 1 and to go from 4 to 1 you have to subtract 3 for there we have all the information we need what is change in Y over change in X well it's going to be our change in Y is negative 3 and our change in X is 1 so our slope is negative 3 divided by 1 is negative 3 let's do another example here we are asked what is the slope of the line that contains these points so pause this video and see if you can figure it out or this is a pause the video again and see if you can figure it out all right so remember slope is equal to change in Y over change in X and we should be able to pick any two of these pairs in order to figure that out if we assume that this is indeed a line well just for variety let's pick these middle two pairs so what's our change in X to go from 1 to 5 we added 4 and what's our change in Y from 7 to 13 we added six so our change in Y is six when our change in X is four and I got the signs right in both case it's a positive act when x increases Y increased as well so our slope is six fourths and we could rewrite that if we like both six and four divisible by two so let me divide both the numerator and the denominator by two and we get three halves and we're done