Question

даю много баллов решите плиз.​

Answer 1

3.
1)
$(3 - \frac{x + y}{x - y} ) \div ( \frac{3x}{x + y} - 2) = \\ \\ \frac{3x - 3y - x - y}{x - y} \div \frac{3x - 2x - 2y}{x + y} = \\ \\ \frac{2x - 4y}{x - y} \times \frac{x + y}{x - 2y} = \\ \\ \frac{2(x - 2y)}{x - y} \times \frac{x + y}{x - 2y} = \\ \\ \frac{2x + 2y}{x - y} .$
2)
$( \frac{9a - 3b}{a + b} - 1) \div (3 + \frac{a + b}{a - b} ) = \\ \\ \frac{9a - 3b - a - b}{a + b} \div \frac{3a - 3b + a + b}{a - b} = \\ \\ \frac{8a - 4b}{a + b} \times \frac{a - b}{4a - 2b} = \\ \\ \frac{4(2a - b)}{ a + b} \times \frac{a - b}{2(2a - b)} = \\ \\ \frac{2a - 2b}{a + b} .$
4.
1)
$( \frac{2 {m}^{2} }{ {m}^{2} - {n}^{2} } - \frac{m}{m - n} ) \div \frac{ {m}^{3} }{mn + {n}^{2} } = \\ \\ \frac{2 {m}^{2} - {m}^{2} - mn }{ {m}^{2} - {n}^{2}} \times \frac{mn + {n}^{2} }{ {m}^{3} } = \\ \\ \frac{ m(m - n) }{(m + n)(m - n)} \times \frac{n(m + n)}{ {m}^{3} } = \\ \\ \frac{n}{ {m}^{2} } .$
2)
$\frac{ {y}^{2} }{ {x}^{2} - xy } \div ( \frac{y}{x + y} - \frac{2xy}{ {x}^{2} - {y}^{2} }) = \\ \\ \frac{ {y}^{2} }{x(x - y)} \div \frac{xy - {y}^{2} - 2xy }{(x - y)(x + y)} = \\ \\ \frac{ {y}^{2} }{x(x - y)} \times \frac{(x - y)(x + y)}{ y( - y - x) } = \\ \\ - \frac{ {y}^{2} }{x(x - y)} \times \frac{(x - y)(x + y)}{y(x + y)} = \\ \\ - \frac{ {y}^{2} }{x(x - y)} \times \frac{x - y}{y} = \\ \\ - \frac{y}{x} .$