[(-5)^9-(-5)^7]:(5^7-2×5^6-3×5^5)=
=[-1953125+78125)]:(78125-2×15625-3×3125)=
=[ -1875000]:(78125-31250-9645)=
- 1875000:37230= -50
$ [(-5)^9 - (-5)^7] : (5^7 - 2 \cdot 5^6 -3 \cdot 5^5) = $
$ = [-(5)^9 + (5)^7] : [5^5(5^2 - 2\cdot 5 - 3)] = $
$ = 5^7[ 1- 5^2] : [5^5(5^2 - 2\cdot 5 - 3)] = $
$ 5^2 (1 - 25) : 12 = $
$ - 2 \cdot 5^2 = - 50 $
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$\dfrac{(-5)^9-(-5)^7}{5^7-2·5^6-3·5^5}=$
$= \dfrac{-1953125-(-78125)}{78125-2·15625-3·3125}=$
$= \dfrac{-1953125+78125}{78125-31250-9375}=$
$= \dfrac{-1875000}{37500}= -50$