25 БАЛЛОВ Помогите с решением.Преобразование рациональных выражений 1. Выполните...

А)
$\frac{x + {x}^{2} }{1 + \frac{1}{x} } = \frac{x(1 + x)}{ \frac{x + 1}{x} } = \frac{ {x}^{2}(1 + x) }{x + 1} = {x}^{2}$
б)
$( {x}^{2} - 4) \div \frac{3 {x}^{2} + 6x }{ {x}^{3} } \times \frac{12}{4 - 4x} + 2x = (x - 2)(x + 2) \div \frac{3x(x + 2)}{ {x}^{3} } \times \frac{12}{4(1 - x)} + 2x = \frac{(x - 2)(x + 2) \times {x}^{3} \times 12 }{3x(x + 2) \times 4(1 - x)} + 2x = \frac{(x - 2) {x}^{2} \times 4 }{4(1 - x)} + 2x = \frac{ {x}^{2} (x - 2) + 2x(1 - x)}{1 - x} = \frac{ {x}^{3} - 2 {x}^{2} + 2x - 2 {x}^{2} }{1 - x} = \frac{ {x}^{3} - 4 {x}^{2} + 2x }{1 - x}$
в)
$\frac{x + 9}{x - 6} \div \frac{3x ^{2} - 18x + 27}{ {x}^{2} - 36 } = \frac{(x + 9)(x - 6)(x + 6)}{(x - 6) \times 3( {x}^{2} - 6x + 9)} = \frac{(x + 9)(x + 6)}{3(x - 3 )^{2} }$
2.
$2 a+ 3b =0 .6(5a + 3b) \\ 2a + 3b = 3a + 1.8b \\ 3b - 1.8b = 3a - 2a \\ a = 1.2b \\ - - - - - - - - - - - - - \\ \frac{ {a}^{2} + 3ab}{ {b}^{2} } = \frac{a(a + 3b)}{ {b}^{2} } = \frac{1.2b(1.2b + 3b)}{ {b}^{2} } = \frac{1.2 \times 4.2b}{b} = 5.04$