Math $255$

$2.$ Find the derivative.

$($a$)f(x)=(3-x)(\frac{4}{x^2}-5)$

$($b$)g(x)=\frac{4x^2-x2}{3-4x}$

$3.$ Find an equation of the tangent line to the graph of $f(x)=\frac{2x1}{x-1}$ at the point $(2,5).$