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)


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