indefinite integration

1. using the substitution u=1/x , find ∫ dx/((x^3 √(x^4+1))
2. using the substitution u=x^(1/2) +1 , find ∫(((x^(1/2)-1)) / ((x^(1/2)+1))) dx


3. ∫sin2x/(1+sin^2x)^2 dx

4. ∫ x dx/ √((x+1)(x+7))