4) Simplify the expression \( \frac{x^7 + x^5}{x^7 + x^9} \).

\( \frac{x^7 + x^5}{x^7 + x^9} = \frac{x^5(x^2 + 1)}{x^7(1 + x^2)} = \frac{x^5}{x^7} = \frac{1}{x^2} \) (assuming \( x
eq 0 \)).