What is the integrating factor for the linear ODE (x+1)y′+y=x(x+1)y' + y = x(x+1)y′+y=x?
x+1x+1x+1
ln(x+1)\ln(x+1)ln(x+1)
1/(x+1)1/(x+1)1/(x+1)
ex+1e^{x+1}ex+1