Question

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Answer 1

$7(z - b)$

Ответ:

$( \frac{z}{b} - \frac{b}{z} ) \times \frac{7zb}{z + b} =\left(\frac{zz}{bz}-\frac{bb}{bz}\right)\times \left(\frac{7zb}{z+b}\right) =\frac{zz-bb}{bz}\times \left(\frac{7zb}{z+b}\right) =\frac{z^{2}-b^{2}}{bz}\times \left(\frac{7zb}{z+b}\right) =\frac{\left(z^{2}-b^{2}\right)\times 7zb}{bz\left(z+b\right)} =\frac{7\left(z^{2}-b^{2}\right)}{z+b} =\frac{7\left(z+b\right)\left(z-b\right)}{z+b} =7\left(z-b\right)$