Question

упрости выражение....​

Answer 1

$\displaystyle\bf\\\frac{a}{1-b} -\frac{a}{1+b} =\frac{a\cdot(1+b)-a\cdot(1-b)}{(1-b)(1+b)}=\frac{a+ab-a+ab}{1-b^{2} } =\frac{2ab}{1-b^{2} }$