Jambmaths question:
A polynomial in x whose zero are –2, –1 and 3 is
Option A:
${{x}^{3}+7x+6$
Option B:
${x}^{3}-7x+6$
Option C:
${x}^{3}}-7x-6$
Option D:
${x}^{3}+7x-6$
Jamb Maths Solution:
$\begin{align} & \text{Since }\text{2},\text{ }\text{1 and 3 are the zeros of the function},\text{ it means} \\ & f(x)=(x+2)(x+1)(x-3) \\ & f(x)=({{x}^{2}}+3x+2)(x-3) \\ & f(x)={{x}^{3}}+3{{x}^{2}}+2x-3{{x}^{2}}-9x-6 \\ & f(x)={{x}^{3}}-7x-6 \\\end{align}$
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