Question

Write an equation in slope-intercept form for the line through two points.

1. (7,8) and (-7, 6)
2. (-1, 2) and (4, -23)

Answer 1

Using y = mx + b, first we need the slope m

m = (8-6)/(7-(-7))
= 2/14 = 1/7
sofar: y = (1/7)x + b
sub in (7,8)
8 = (1/7)(7) + b
8 = 1 + b
7 = b

y = (1/7)x + 7

I usually check, by testing with the point that was not used in the substitution , in this case (-7,6)
LS = 6
RS = (1/7)(-7) + 7
= -1 + 7
= 6
= LS

My equation is correct.

Do the 2nd problem the same way, let me know what you get.

Answer 2

2. When I was attempting to find the slope, I received 2/22 as the fraction. However, I do not know nor remember how to reduce it.

Answer 3

look for a number which divides into both of them, in this case 2

2/22 = 1/11

<b>HOWEVER</b>, how did you ever get 2/22 ?
Remember, you have to start with the y's on top and the x's in the denominator

slope = (2 - (-23))/(-1-4)
= 25/-5
= -5

so y = 5x + b
using (-1,2)
2 = -5(-1) + b
2 = 5 + b
-3 = b

y =-5x - 3

does (4, -23) satisfy this??

Answer 4

2)
(-1,2 ) and (4,-23)

m = (-23-2)/(4-(-1) = -25/5

m = -5

y = mx + b

2 = (-5)(-1) + b
2 = 5 + b
2-5 = 5-5 + b
-3 = b

y = mx + b

y = -5x -3