Question

The value(s) of $x$ satisfying the equation
$2|x^2|-x-21=0\text{are}:$

• A. $\frac{7}{2}$
• B. $-3$
• C. $-\frac{3}{2}$
• D. $-7$

Answer 1

Answer: (A), (B)

$-3$

Given equation:
$2|x^2|-x-21=0$
Since, we know $x^2$ is a positive number.
$\Rightarrow |x^2|=x^2$
Thus, our equation becomes:
$\Rightarrow 2x^2-x-21=0$
$\Rightarrow 2x^2+6x-7x-21=0$
$\Rightarrow 2x(x+3)-7(x+3)=0$
$\Rightarrow (x+3)(2x-7)=0$
$\Rightarrow x=-3\text{Or}x=\frac{7}{2}$