Question

求不定积分∫x^3/根号下(9+X^2) dx

Answer 1

∫x^3dx/√(9+x^2)

=(1/2)∫x^2dx^2/√(9+x^2)

=(1/2)∫∫√(9+x^2)dx^2-(9/2)∫dx^2/√(9+x^2)

=(1/3)√(9+x^2)^3 -9√(x^2+9) +C