Find the following derivatives using the difference quotient formula.
f : x \longmapsto \dfrac{2x^2}{1-x} for x=0
f : x \mapsto \dfrac{2x^2 + 1}{3x^2 + 2} for x=0
f : x \longmapsto \dfrac{x}{x^2+1} for x=1
f : x \mapsto 2x^2 + 2x + 6 for x=-2
f : x \mapsto x^2 - 4x + 6 for x=2
f : x \mapsto \dfrac{\left(x + 2\right)^2 + 3}{x - 3} for x=-3
f : x \mapsto \dfrac{5-x}{10-3x^2} for x=0