17) P3-18) 2x²+x+2xy+y 1-p2 1-4x2

7) $$ \frac{p^3-1}{1-p^2} = \frac{(p-1)(p^2+p+1)}{(1-p)(1+p)} = \frac{-(1-p)(p^2+p+1)}{(1-p)(1+p)} = \frac{-(p^2+p+1)}{1+p} $$

Ответ: $$\frac{-(p^2+p+1)}{1+p}$$