// 2 2 \
|| x *y | 2 2| |
|| ------------ for |x *y | < 1|
|| 2 |
|| / 2 2\ |
|| \1 - x *y / |
7 || |
-x*y *|< oo |
|| ___ |
|| \ ` |
|| \ n |
|| ) / 2 2\ otherwise |
|| / n*\x *y / |
|| /__, |
\\n = 1 /
$$- x y^{7} \left(\begin{cases} \frac{x^{2} y^{2}}{\left(- x^{2} y^{2} + 1\right)^{2}} & \text{for}\: \left|{x^{2} y^{2}}\right| < 1 \\\sum_{n=1}^{\infty} n \left(x^{2} y^{2}\right)^{n} & \text{otherwise} \end{cases}\right)$$
-x*y^7*Piecewise((x^2*y^2/(1 - x^2*y^2)^2, |x^2*y^2| < 1), (Sum(n*(x^2*y^2)^n, (n, 1, oo)), True))