Q3 of 86 Page 48

Show that (x – 2), (x + 3) and (x – 4) are factors of x3 – 3x2 – 10x + 24.

Let f(x) = x3 – 3x2 – 10x + 24


By Factor Theorem, we know that,


If p(x) is a polynomial and a is any real number, then g(x) = (x– a) is a factor of p(x), if p(a) = 0


For checking (x – 2) to be a factor, we will find f(2)


f(2) = (2)3 – 3(2)2 – 10(2) + 24


f(2) = 8 – 12 – 20 + 24


f(2) = 0


So, (x–2) is a factor.


For checking (x + 3) to be a factor, we will find f(–3)


f(–3) = (–3)3 – 3(–3)2 – 10(–3) + 24


f(–3) = –27 – 27 + 30 + 24


f(–3) = 0


So, (x+3) is a factor.


For checking (x – 4) to be a factor, we will find f(4)


f(4) = (4)3 – 3(4)2 – 10(4) + 24


f(4) = 64 – 48 – 40 + 24


f(4) = 0


So, (x–4) is a factor.


(x – 2), (x + 3) and (x – 4) are factors of x3 – 3x2 – 10x + 24


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