Question

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

Answer 1

First we need to find the slope: 

Slope formula=$\frac{y2-y1}{x2-x1}$

Plug in your given values from the coordinate 
Slope =$\frac{1-(-3)}{3-1}$

When we have 2 "-"'s together they turn into a + sign so we add. 
Slope =$\frac{1+3=4}{3-1=2}$
Slope =$\frac{4}{2}$

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)