Q7 of 86 Page 48

Factorize

x3 + 13x2 + 32x + 20

Let p(x) = x3 + 13x2 + 32x + 20


By trial, we find that p(–1) = 0, so by Factor theorem,


(x + 1) is the factor of p(x)


When we divide p(x) by (x + 1), we get x2 + 12x + 20.


Now, (x2 + 12x + 20) is a quadratic and can be solved by splitting the middle terms.


We have x2 + 12x + 20= x2 + 10x + 2x + 20


x (x + 10) + 2 (x + 10)


(x + 2)(x + 10)


So, x3 + 13x2 + 32x + 20 = (x + 1)(x + 2)(x + 10)


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