a) $\frac{2a^3+4a^2}{a^2-4}=\frac{...}{a-2}$
Ta có: $\frac{2a^3+4a^2}{a^2-4}=\frac{2a^2(a+2)}{(a-2)(a+2)}=\frac{2a^2}{a-2}$
⇒$\frac{2a^3+4a^2}{a^2-4}=\frac{2a^2}{a-2}$
b)$\frac{5(x+y)}{3}=\frac{5x^2-y^2}{...}$
⇔$\frac{5(x+y)}{3}=\frac{5(x-y)(x+y)}{...}$
⇒$\frac{5(x+y)}{3}=\frac{5(x-y)(x+y)}{3(x-y)}$