Solve the equation.

x2 - x - 12 = 0

A) x = 4

B) x = - 3

C) x = - 3 or x = 4

D) x = - 4 or x = 3

C

Step-by-step explanation:

In this technique, if we have to factorise an expression like ax2+bx+c, we need to think of 2 numbers such that:

N1⋅N2=a⋅c=1⋅-12=-12

AND

N1+N2=b=-1

After trying out a few numbers we get N1=3 and N2=-4

3⋅-4=-12, and 3 + (-4) = -1

x2-x-12=x2-4x+3x-12

x (x-4) + 3 (x-4) = 0

(x+3) (x-4) = 0

Now we equate the factors to zero.

x+3=0, x=-3

x-4=0, x=4