8) $$ \frac{2x^2+x+2xy+y}{1-4x^2} = \frac{2x^2+x+2xy+y}{(1-2x)(1+2x)} = \frac{x(2x+1)+y(2x+1)}{(1-2x)(1+2x)} = \frac{(x+y)(2x+1)}{(1-2x)(1+2x)} = \frac{x+y}{1-2x} $$
Ответ: $$\frac{x+y}{1-2x}$$