Giải các phương trình: a) $\frac{3}{x-1} + \frac{5}{x+1} =\frac{2}{x^2 - 1}; $ b) $\frac{5-x}{4x^2 - 8x} + \frac{7}{8x} = \frac{x-1}{2x(x+2)} + \frac{1}{8x - 16} $ c) $\frac{1}{x+2} + \frac{1}{x^2 - 2x} = \frac{8}{x^3 - 4x} $ d) $1+ \frac{45}{y^2 - 8y + 16} = \frac{14}{y-4} $; e) $\frac{1}{1-\frac{1}{1-\frac{1}{x} } } = 3 $ f) $\frac{1- \frac{x-2}{x+2} }{2+ \frac{x}{x+2} } = \frac{1}{4} $. g) $\frac{\frac{x+1}{x-1} - \frac{x-1}{x+1} }{1+ \frac{x+1}{x-1} } = \frac{1}{2} $
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