How to write the equation of a line that passes through the points (-1,3) and (1,-1)

y = -2x + 1

Solution:

To find the the equation use first find the slope using the equation:

m= y2-y1/x2-x1

m = -1-3/1-(-1)

m = -4/2

m = -2

Using the equation below,

y = mx + b  

y = y coordinate  

m = slope  

x = x coordinate  

b = y intercept  

so to write the equation of line we need to find the y-intercept (b)  

substitute the slope (-2) and any of the given pair of coordinates ,  right now i will be using (1,-1)

y = mx + b  

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

-1+2 = b

1 = b

So the line of equation,

y = mx + b  

y = -2x + 1