Question

When $x=2,$ the value of the expression $4x^2+\frac{9}{x^2}-12$ is:

• A. $\frac{25}{4}$
• B. $\frac{-4}{25}$
• C. $\frac{4}{25}$
• D. $\frac{-25}{4}$

Answer 1

The correct option is A $\frac{25}{4}$

$4x^2+\frac{9}{x^2}-12$

$={(2x-\frac{3}{x})}^2$

$={((2\times 2)-\frac{3}{2})}^2$

$={(4-\frac{3}{2})}^2$

$={\left(\frac{5}{2}\right)}^2$

$=\frac{25}{4}$