Question

$( frac{a}{a+4} - frac{a}{a-4} )* frac{a+4}{a}$
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Answer 1

$( frac{ alpha }{ alpha +4} - frac{ alpha }{ alpha -4})* frac{ alpha +4}{ alpha } =- frac{8}{a-4} \ 1) frac{ alpha }{ alpha +4} - frac{ alpha }{ alpha -4} = frac{a(a-4)}{(a+4)(a-4)} - frac{a(a+4)}{(a+4)(a-4)} = frac{ alpha ^{2} -4a}{(a+4)(a-4)} - frac{ alpha ^{2}+4a }{(a+4)(a-4)}= \ = frac{ alpha ^{2}-4 alpha - alpha^{2} -4a}{(a+4)(a-4)} = -frac{8a}{ (a+4)(a-4)} \ 2)- frac{8 alpha*(a+4) }{(a+4)(a-4)*a} =- frac{8}{a-4}$