Question 179016
First we find the slopw (m)
m=(y2-y1)/(x2-x1)
m=(1-9)/(1-3)
m=-8/-2
m=4 for the slope
Y=mX+b
Now we replace X & Y by one set of points & sole for the Y intercept (b)
1=4*1+b
1=4+b
b=1-4
b=-3 for the Y intercept.
Y=4x-3 is the line equation.
Proof:
{{{ graph( 300, 200, -6, 5, -10, 10, 4x -3) }}} (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, 4x -3).