Question

If $(x+1)$ is a factor of $3x^2+kx+4$, then k =_________________

• A. $3$
• B. $6$
• C. $-7$
• D. $7$

Answer 1

Answer: (D)

$7$

It is given that $x+1$ is a factor of $3x^2+kx+4=f\left(x\right)\left(say\right)$

Then, $f(-1)=0$

$\Rightarrow 3(-1{)}^2+k(-1)+4=0$

$\Rightarrow 3-k+4=0$

$\Rightarrow k=7$

Hence, $\text{D}$ is a correct option.