Question

На 4 сделайте срочно.50 балов

Answer 1

$1.( frac{x+5y}{ x^{2} -5xy} - frac{x-5y}{ x^{2} +5xy} ) * frac{25y^{2}- x^{2} }{5y^{2} } = (frac{(x+5y)^{2}-(x-5y)^{2} }{x(x-5y)(x+5y)}) * frac{(5y-x)(5y+x)}{5y^{2} } }$=$frac{(x+5y-x+5y)(x+5y+x-5y)}{-x(5y-x)} * frac{5y-x}{5y^{2} } = frac{10y*2x}{-x} * frac{1}{5 y^{2} } = frac{4x}{-5xy^{2} } =- frac{4}{5 y^{2} }$
2.$(a+1+ frac{1}{a-1} ): frac{ a^{2} }{1-2a+ a^{2} } = frac{ a^{2}-a+a-1+1 }{a-1} * frac{(a-1)^{2} }{ a^{2} } = a^{2} * frac{a-1}{ a^{2} } =a-1$
3.$( frac{3}{(2-x)^{2} } + frac{2}{ x^{2} -4} )*(x-2) ^{2} - frac{5x}{x+2} =( frac{2(x+2)}{(x-2) ^{2}(x+2) } + frac{2(x-2)}{(x-2) ^{2}(x+2) } )$*$(x-2) ^{2} - frac{5x}{x+2} = frac{2x+4+2x-4}{x+2} - frac{5x}{x+2} = frac{4x-5x}{x+2} =- frac{x}{x+2}$  
4.$frac{1- frac{3}{c} }{ frac{6c-9}{c} -c} = frac{ frac{c-3}{c} }{ frac{6c-9- c^{2} }{c} } =(c-3)*(6c-9- c^{2} )=(c-3)*6(c-3)- c^{2} =$$6(c-3)^{2} -c^{2} =(6c-18-c)(6c-18+c)=(5c-18)(7c-18)$

Answer 2

где 5