Question

Answer 1

a) \(ĐKXĐ:x\ne\pm1\)

b) \(M=\left(\dfrac{x+1}{2x-2}+\dfrac{3}{x^2-1}-\dfrac{x+3}{2x+2}\right).\dfrac{x^2-1}{15}\)

\(=\left[\dfrac{\left(x+1\right)^2}{2\left(x-1\right)\left(x+1\right)}+\dfrac{6}{2\left(x-1\right)\left(x+1\right)}-\dfrac{\left(x+3\right)\left(x-1\right)}{2\left(x-1\right)\left(x+1\right)}\right].\dfrac{\left(x-1\right)\left(x+1\right)}{15}\)

\(=\left[\dfrac{x^2+2x+1+6-\left(x^2+2x-3\right)}{2\left(x-1\right)\left(x+1\right)}\right].\dfrac{\left(x-1\right)\left(x+1\right)}{15}\)

\(=\left(\dfrac{4}{2\left(x-1\right)\left(x+1\right)}\right).\dfrac{\left(x-1\right)\left(x+1\right)}{15}=\dfrac{2}{15}\)

Vậy...