SOLUTION: (X,-4) AND (2,8); M=-3

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Question 1176519: (X,-4) AND (2,8); M=-3
Found 2 solutions by MathLover1, greenestamps:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

given:
(x,-4) and (2,8)
m=-3
m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29

-3=%288-%28-4%29%29%2F%282-x%29
-3=%288%2B4%29%2F%282-x%29
-3=12%2F%282-x%29
-3%282-x%29=12
%282-x%29=12%2F-3
2-x=-4
2%2B4=x
x=6
then (x,-4) is (6,-4)




Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


You should know how to solve the problem with formal algebra, as shown by the other tutor.

But I always encourage students to understand what they are doing, instead of just plugging numbers into formulas. You get better mental exercise, and you learn the mathematics better, if you solve the problem informally.

The slope of a line tells you how much you go up or down as you move 1 unit to the right.

Given a negative slope and y coordinates of -4 and 8, we can conclude that (2,8) is to the left of (x,-4).

The slope of -3 means you go down 3 every time you go 1 unit to the right. The difference in the y coordinates of the two points is -12, which is 4 times the slope of -3. So the change of -12 in the y coordinates means you moved -12/-3 = 4 units to the right.

And 4 units to the right of x=2 is x=6.

ANSWER: x=6