Question

срочно нужно 1 вариант ...... ДАЮ 50 баллов​

Answer 1

Ответ:

Объяснение:

1.

$\frac{x+7}{x-2}$      ОДЗ: x-2≠0     x≠2    ⇒    x∈(-∞;2)U(2;+∞).

2.

$\frac{5-a}{a^{2} -8a+16} +\frac{6}{5a-20} =\frac{5-a}{(a-4)^{2} } +\frac{6}{5*(a-4)} =\frac{(5-a)*5+6*(a-4)}{5*(a-4)^{2} } =\\=\frac{25-5a+6a-24}{5*(a-4)^{2} } =\frac{a+1}{5*(a-4)^{2} } .$

3.

$\frac{5x^{2}-10xy+5y^{2} }{2x^{2} -2xy+2y^{2} } :\frac{4x-4y}{10x^{3} +10y^{3} } =\frac{5*(x^{2}-2xy+y^{2}) }{2*(x^{2} -xy+y^{2}) } *\frac{10*(x^{3} +y^{3})}{ 4*(x-y)} =\frac{5*(x-y)^{2} *10*(x+y)*(x^{2} -xy+y^{2}) }{2*(x^{2}-xy+y^{2} )*4*(x-y) } =\\=\frac{25*(x-y)*(x+y)}{4} =\frac{25*(x^{2} -y^{2}) }{4}=\frac{25*(7^{2}-3^{2}) }{4} =\frac{25*(49-9)}{4} =\frac{25*40}{4} =25*10=250.$4.

$\frac{a}{b} =3;\frac{b}{c} =8\\\frac{a}{b}*\frac{b}{c} =24\\\frac{a}{c} =24.$