Question

9а²/а²-25-9/а+5
При а=корень 23
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Answer 1

$frac{9a^2}{a^2-25}-frac9{a+5}=frac{9a^2}{(a-5)(a+5)}-frac9{a+5}=frac{9a^2-9(a-5)}{(a-5)(a+5)}=frac{9a^2-9a+45}{(a-5)(a+5)}=\=frac{9(a^2-a+5)}{a^2-25}\ frac{9(a^2-a+5)}{a^2-25}=frac{9((sqrt{23})^2-sqrt{23}+5)}{(sqrt{23})^2-25}=frac{9(23-sqrt{23}+5)}{23-25}=frac{9(28-sqrt{23})}{-2}=-frac{9(28-sqrt{23})}{2}$