Question

The graph of $x^2-\sqrt{5}x-2$ has its minimum value at what approximate value of $x$?

• A. $0.83$
• B. $1.12$
• C. $1.21$
• D. $1.35$
• E. $2.47$

Answer 1

The correct option is B $1.12$

We know that for quadratic equation $a{x}^2+bx+c=0$, minimum value is given by $\frac{-b}{2a}$
Comparing given equation $x^2-\sqrt{5}x-2=0$ with standard form, we get

$b=-\sqrt{5}$ and $a=1$
So, minimum value is
$=\frac{-(-\sqrt{5})}{2\times 1}$
$=\frac{\sqrt{5}}{2}$
$=1.118$
$=1.12$

Hence, the answer is $1.12$.