Помогите пожалуйста!!!!!Срочно надо!!!!

1)
$\frac{9 {b}^{2} }{2a - 3b} + \frac{4 {a}^{2} }{3b - 2a} = \frac{9 {b}^{2} }{2a - 3b} + \frac{4 {a}^{2} }{ - (2a - 3b)} = \frac{9 {b}^{2} }{2a - 3b} - \frac{4 {a}^{2} }{2a - 3b} = \frac{9 {b}^{2} - 4 {a}^{2} }{2a - 3b} = \frac{(3b - 2a)(3b + 2a)}{ - (3b - 2a)} = - (3b + 2a) = - 3b - 2a$
2)
$\frac{25 {n}^{2} }{6m - 5n} + \frac{36 {m}^{2} }{5n - 6m} = \frac{25 {n}^{2} }{6m - 5n} + \frac{36 {m}^{2} }{ - (6m - 5n)} = \frac{25 {n}^{2} }{6m - 5n} - \frac{36 {m}^{2} }{6m - 5n} = \frac{25 {n}^{2} - 36 {m}^{2} }{6m - 5n} = \frac{(5n - 6m)(5n + 6m)}{ - (5n - 6m)} = - (5n + 6m) = - 5n - 6m$
3)
$\frac{2a}{7a - 5} - \frac{4a}{5 - 7a} = \frac{2a}{7a - 5} - \frac{4a}{ - (7a - 5)} = \frac{2a}{7a - 5} + \frac{4a}{7a - 5} = \frac{6a}{7a - 5}$
4)
$\frac{a}{9 {a}^{2} - 4 } - \frac{a}{4 - 9 {a}^{2} } = \frac{a}{9 {a}^{2} - 4} - \frac{a}{ - (9 {a}^{2} - 4) } = \frac{a}{9 {a}^{2} - 4 } + \frac{a}{9 {a}^{2} - 4} = \frac{2a}{9 {a}^{2} - 4}$