Respuesta :

First we have to calculate for slope, 
m = y2-y1 / x2-x1
m = 1+2 / 1 - 2
m = 3 / -1
m = -3

Now, y-y1 = m(x-x1)
y - 1 = -3(x - 1)
y - 1 = -3x + 3
y = -3x + 4

In short, Your Answer would be: y = -3x + 4

Hope this helps!