Question

упражнение 88. Срочно помогите

Answer 1

$\displaystyle\bf\\5x-10y=2 \ |:5 \ \ \ \Rightarrow \ \ \ x-2y=0,4\\\\1)\\\\\frac{10}{x-2y} =\frac{10}{0,4} =\frac{100}{4} =25\\\\2)\\\\x-2y=0,4 \ |\cdot 3 \ \ \ \Rightarrow \ \ \ 3x-6y=1,2\\\\\frac{14}{3x-6y} =\frac{14}{1,2} =\frac{140}{12} =11\frac{8}{12} =11\frac{2}{3} \\\\3)\\\\\frac{7x^{2} -28y^{2} }{8x+6y} =\frac{7\cdot(x^{2} -4y^{2} )}{8\cdot(x+2y)} =\frac{7\cdot(x-2y)\cdot(x+2y)}{8(x+2y)} =\\\\\\=\frac{7\cdot(x-2y)}{8} =\frac{7\cdot 0,4}{8} =0,35$

$\displaystyle\bf\\4)\\\\\frac{0,6x-1,2y}{5x^{2} -20xy+20y^{2} } =\frac{0,6\cdot(x-2y)}{5\cdot(x^{2} -4xy+4y^{2} )} =\\\\\\=\frac{0,6\cdot(x-2y)}{5\cdot(x-2y)^{2} } =\frac{0,6}{5\cdot(x-2y)} =\frac{0,6}{5\cdot 0,4} =\frac{0,6}{2} =0,3$