Помогите пожалуйста!!! 7а/6с - 49а^2+36c^2/42ac + 6c-49a/7а

Решите задачу:

$\frac{7a}{6c} - \frac{49a^2+36c^2}{42ac} + \frac{6c-49a}{7c} = \frac{7a*7c}{6c*7a} - \frac{49a^2+36c^2}{42ac} + \frac{(6c-49a)*6c}{7a*6c} =\frac{49ac}{42ac} - \frac{49a^2+36c^2}{42ac} + \frac{36c^2-294ac}{42ac} =\frac{49ac- 49a^2-36c^2+36c^2-294ac}{42ac} =\frac{- 49a^2-245ac)}{42ac} =\frac{7a(- 7a-35c))}{42ac} =\frac{- 7a-35c}{6c} =\frac{- (7a+35c)}{6c} = -\frac{7a+35c}{6c}$