Question

Find an equation for the line that passes through the points (3,-5) and (-5,5).

Answer 1

y=-5/4 + -1.25

Explanation:

y1 - y2 over x1 -x2

5- -5 =10

-5-3 =-8

simplify: -10/8 which is -5/4 *THAT IS YOUR SLOPE*

Now to find the y intercept pick a point. I chose (-5,5) and plug in for y=mx+b

y will be 5 ; m is your slope so -5/4 ; x is -5 and we don't have out b yet.

5=-5/4(-5) + b

multiply -5/4 and -5 = 6.25

then just subtract -5 and -6.25 = -1.25 which is your y intercept

y= -5/4 + -1.25

Answer 2

y = -⁵/₄x -⁵/₄

Explanation:

(a) Slope

The point-slope formula for a straight line is

y₂ - y₁ = m(x₂ - x₁)

The line goes through the points (3, -5) and (-5,5).

5 – (-5) = m(-5 – 3)

10 = -8m

m = -⁵/₄

(b) y-intercept

y = mx + b

Use the point (5, -5)

-5 = -⁵/₄×5 + b

-5 = -²⁵/₄ + b

b = ⁵/₄

∴ y = -⁵/₄x - ⁵/₄