giải phương trình
a) \(\frac{x+1}{x-1}\)-\(\frac{x-1}{x+1}\)=\(\frac{4}{x^2-1}\)
b) \(\frac{8x^2}{3\left(1-4x^2\right)}\)=\(\frac{2x}{6x-3}\)-\(\frac{1+8x}{4+8x}\)
c) \(\frac{3}{4\left(x-5\right)}\)+\(\frac{15}{50-2x^2}\)= - \(\frac{7}{6\left(x+5\right)}\)
d) \(\frac{13}{\left(x-3\right)\left(2x+7\right)}\)+\(\frac{1}{2x+7}\)=\(\frac{6}{x^2-9}\)