Evaluate the function at the given values of the independent variable and simplify.

$f(x)=\frac{6x^2-1}{x^2}$

$($a$)f(2)$

$($b$)f(-2)$

$($c$)f(-x)$

$($a$)f(2)=$

$($Type an integer or a fraction. Simplify your answer.$)$