Answer:
r = -1
Step-by-step explanation:
(y2-y1)/(x2-x1)=m
(r,7)=(x1,y1) and (3,4)=(x2-y2) and m=-3/5
so plug in...
(4-7)/(4-r)=-3/5
then solve for r which will get that r = -1
numerator: 4-7=-3
denominator: 4-r=5 -> 4-5=0+r -> -1=r
Answer:
Solve the 1st equation for y and then you substitute the answer of the y value to the other equation to get the x value
They cancel out each other
Imagine if you were multiplying
-2 * -3
you would get 6
if you did
-2 * 3
you would get -6 because there isn't another - to cancel it out
I learned it that when you have a negative before a negative, put parenthesis around the second number with the negative, so it looks like this
-(-2)
if you look at the -(- it looks like a plus sign
that probably doesn't make much sense but we cancelling it out is just a rule, we don't really know why we do it