Q7 of 64 Page 49

4 is a zero of the cubic polynomial p(x) = x3 — 3x2 — 6x + 8. Find the remaining zeros of p(x).

Given, 4 is a zero of polynomial p(x).


So (x – 4) is the factor of p(x).


Here, dividend polynomial = p(x) = x3 — 3x2 — 6x + 8


and divisor polynomial = s(x) = x – 4.


Coefficients of x3, x2, x and x° are 1, –3, –6 and 8 respectively.


Taking x – 4 = 0 we get x = 4



p(x) = x3 — 3x2 — 6x + 8


= (x – 4) (x2 + x – 2)


= (x – 4) (x2 – x + 2x – 2)


= (x – 4) (x(x – 1) + 2(x –1))


= (x – 4)(x + 2)(x – 1)


To find the remaining zeros, let p(x) = 0


i.e. (x – 4)(x + 2)(x – 1) = 0


The remaining zeros of p(x) are –2 and 1.


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