Question

If $y = ax^2 + b$, then $\frac{dy}{dx}$ at $x = 2$ is equal to

• A. $4a$
• B. $3a$
• C. $2a$
• D. none of these

Answer 1

Answer: (A)

$4a$

Answer 2

We have, $y=ax^{2}+b$ $\Rightarrow \frac{dy}{dx}=2ax$ $\frac{dy}{dx} \bigg|_{x=2}= 2a \times 2 = 4a$