Question

Find an equation of the line that goes through the points (7,-42) and (10,-57). Write your answer in the form

y
=
m
x
+
b
y
=
m
x
+
b
.

Answer 1

y = -5x - 7

Explanation:

What's the slope of this line? Going from (7,-42) to (10,-57), we see x increasing by 3 and y decreasing by 15. Thus, the slope is m = rise / run = -15/3, or m = -5.

Now subst. -42 for y in y = mx + b, -5 for m and 7 for x:

-42 = -5(7) + b. Thus, b = -42 + 35, or b = -7. and the equation of this line is thus y = -5x - 7.

Check: if x = 10, does this equation yield y = -57? Yes

Answer 2

y=-5x-7. I'm almost certain but you never know