Answer:
x = 3  or  x = - 6
Step-by-step explanation:
Factor and Solve. x^2 + 3x - 18 = 0
We can use the Diamond method of factoring.
Factor -18 = 6 * -3;    and  3 = 6 + -3
so
x^2 + 3x - 18 = x^2 -3x + 6x - 18  = 0
= (x^2 -3x)   +  ( 6x - 18)  = 0
= (x^2 -3x)   +  ( 6x - 18)  = 0
= x(x - 3)  + 6*(x - 3) =0 
= (x - 3)*(x + 6) = 0
so  Either  x - 3 = 0   or   x + 6 = 0
x = 3  or  x = - 6