Question

If the function$f\left(x\right)=x^2-ax+4$ is monotonic increasing in the open interval$(2,+\infty )$ then $a$ is

• A. $2$
• B. $4$
• C. $1$
• D. $1/2$

Answer 1

Answer: (B)

$4$

$f^{\prime }\left(x\right)>0$ for monotonically increasing function.
$f^{\prime }\left(x\right)=2x-a>0$ in $(2,\infty )$
$\Rightarrow a=4$