Question 7

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Jambmaths question: 

If x +1 is a factor of ${{x}^{3}}+3{{x}^{2}}+mx+4$ find the value of m

Option A: 

8

Option B: 

6

Option C: 

–8

Option D: 

–6

Jamb Maths Solution: 

$\begin{align}  & \text{Let }f(x)={{x}^{3}}+3{{x}^{2}}+mx+4 \\ & \text{If }x+1\text{ is a factor, then } \\ & f(-1)=0 \\ & f(-1)={{(-1)}^{3}}+3{{(-1)}^{2}}+m(-1)+4=0 \\ & -1+3-m+4=0 \\ & m=6 \\\end{align}$

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