How would you factor out x(x-4)=12

x(x - 4) = 12

First "unfactor" the left side.

x*x - x*4 = 12

x² - 4x = 12

 

Subtract 12 from both sides.

x² - 4x - 12 = 0

 

Factor it back with the 12 included this time.

(x - 6)(x + 2) = 0

 

If that is all the instructions say do, stop there...but if you want to solve for x, set each factor = 0

x - 6 = 0     and      x + 2 = 0

x = 6          and      x = -2