Question

A function is given as $y=5x^2-10x$, then

• A. Maximum value of y is 10
• B. Minimum value of y is -5
• C. Maximum value of y is 0
• D. Maximum value of y occurs at x = 1

Answer 1

The correct option is B Minimum value of y is -5

By maxima or minima $\Rightarrow \frac{dy}{dx}=0$
$\Rightarrow 10x-10=0\Rightarrow x=1$
At $x=1,\frac{d^{2}y}{d{x}^2}=10$ which is positive.
$\therefore Atx=1,$ there is a minima.
$y_{min}=y\left(1\right)=5-10=-5$.