Question

Упростить выражение !

Answer 1

$( frac{x+3}{ x^{2} -3x} + frac{x-3}{ x^{2} +3x} )* frac{9x- x^{3} }{ x^{2} +9} = \ frac{(x+3)(x+3)+(x-3)(x-3)}{x*(x-3)*(x+3)} * frac{9x- x^{3} }{ x^{2} +9} = \ frac{2 x^{2} +18}{x( x^{2} -9)} * frac{x(9- x^{2}) }{x^{2} +9} = \ frac{2}{-1} =-2$


$( frac{1}{x} + frac{1}{y})* frac{2xy}{ x^{2} +2xy + y^{2} } = \ frac{x+y}{xy} * frac{2xy}{ (x+y)^{2} } = \ frac{2}{x+y}$