Find the slope of a line tangent to the curve $\displaystyle y = \frac{4}{x^2} - 2x^2$ at $\displaystyle (-1, 2)$

My Work:

$\displaystyle \frac{f'(x)g(x) - f(x)g'(x)}{g(x)^2}$

$\displaystyle \frac{-8x}{x^4} - 4x$

$\displaystyle m = 12$

Hows it look?