Factorize each of the following quadratic polynomials by using the method of completing;
x2 + 12x + 20
Coefficient of x2 = 1
Therefore, we have
x2 + 12x + 62 – 62 + 20 (Adding and subtracting 62)
= (x + 6)2 – 42 (Completing the square)
= (x + 6 + 4) (x + 6 – 4)
= (x + 10) (x + 2)
= 4 [x - 
+ 1] [x - 
– 1]
= (2x – 1) (2x – 5)
5