Factorize each of the following quadratic polynomials by using the method of completing;
z2 – 4z – 12
Coefficient of z2 = 1
Therefore, we have
z2 – 4z – 12 = z2 – 4z + 22 – 22 – 12 [By adding and subtracting 22]
= (z – 2)2 – 42 (Completing the square)
= (z – 2 + 4) (z – 2 – 4)
= (z + 2) (z – 6)
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