Given,

x² – 4x – 12

Now first find the numbers whose-

Sum = - 4 and

Product = - 12

Required numbers are 6 and 2,

So we get;

x² – 4x – 12

= x² – 6x + 2x – 12

= x(x – 6) + 2(x – 6)

= (x – 6)(x + 2)