Question

Вычислите
${8}^{ - 2} - ( \frac{8}{9}) {}^{ - 1}$
​

Answer 1

ТЕОРИЯ:

$\boldsymbol{a^-^n=\cfrac{1}{a^n}}$

РЕШЕНИЕ:

$\displaystyle\mathtt{8^-^2-(\dfrac{8}{9})^-^1 \ \ = \ \ \frac{1}{64} - \cfrac{1}{\cfrac{8}{9}} \ \ = \ \ \cfrac{1}{64} - \cfrac{9}{8} \ \ = \\ \\\\\\} \cfrac{1}{64} - \cfrac{9\cdot8}{8\cdot8} \ \ = \ \ \cfrac{1}{64} - \cfrac{72}{64} \ \ = \ \ -\cfrac{71}{64} \ \ = \ \ =\ -1\cfrac{7}{64} \\ \\ \\ \\ \bold{OTBET: -1\cfrac{7}{64}}$