Question

The values of $x$ at the stationary points of $f(x)=x^3+3x^2-2$ are

• A. 0,2
• B. 1,2
• C. 0,-2
• D. 1,1

Answer 1

Answer: (C)

Let $y=f(x)=x^3+3x^2-2$
$\frac{dy}{dx}=3x^2+6x$
$\Rightarrow \frac{d^{2}y}{d{x}^2}=6x+6$
For stationary points $\frac{dy}{dx}=0$
$\Rightarrow 3x(x+2)=0$
$\Rightarrow x=0,-2$