Question

What is an equation in slope-intercept form for the line that passes through the points (1, -3) and (3, 1)?

A. y = 3x + 1
B. y = x - 3
C. y = 2x + 5
D. y = 2x - 5

Answer 1

First we need to find the slope:

Slope formula=
`(y2-y1)/(x2-x1)`

Plug in your given values from the coordinate
Slope =
`(1-(-3))/(3-1)`

When we have 2 "-"'s together they turn into a + sign so we add.
Slope =
`(1+3=4)/(3-1=2)`
Slope =
`(4)/(2)`

Simplify (in this case divide) the slope:
Slope =
`2`

slope-intercept form is:
y=mx+b
Where m=slope
b=y-intercept

So far we have:
y=2x+b

To find b all we have to do is pick any given coordinate and plug it in:
I chose (3,1)

so we plug that in the equation
1=6+b

Now solve for b:
1=6+b
subtract 6 from both sides
b=-5

Final answer:
y=2x-5 (D)