Aufgabe a:
\( \left(\frac{n^{2}}{b^{2}}-\frac{b^{2}}{a^{2}}\right): \frac{a^{2}+b^{2}}{a^{2}+b^{2}} \)
\( \begin{array}{l} {=\frac{a^{2}+a^{2}-b^{2} \cdot b^{2}}{b^{2} a^{2}}: \frac{a^{2}+b^{2}}{a^{2}+b^{2}}} \\ {=\frac{a^{4}-b^{4}}{b^{2} a^{2}}: \frac{a^{2}+b^{2}}{a^{2}, b^{2}}} \end{array} \)
\( a^2 - b^2 \)
Aufgabe b:
\(\begin{aligned} & \frac{1-x^{5}}{x^7}+\frac{1}{x^{2}} \\=& \frac{1}{x^{7}}-\frac{x^{5}}{x^{7}}+\frac{1}{x^{2}} \\=& \frac{1}{x^{7}}-\frac{1}{x^{2}}+\frac{1}{x^{2}} \\=& \frac{1}{x^{7}}=x^{-7} \end{aligned}\)