The line passes through A(1,3) and B(2,-1)

Then:

y-yA = m (x-xA) where m is the slope.

m= (yB-yA)/(xB-xA) = (-1-3)/(2-1) = -4

Then:

y-3 = -4(x-1)

y-3 = -4x + 4

**==> y= -4x +7**

The line passes through A(1,3) and B(2,-1)

Then:

y-yA = m (x-xA) where m is the slope.

m= (yB-yA)/(xB-xA) = (-1-3)/(2-1) = -4

Then:

y-3 = -4(x-1)

y-3 = -4x + 4

**==> y= -4x +7**