y =(x+1)^(x+3) = e^[ln(x+1)^(x+3)] = e^[(x+3)ln(x+1)]
dy/dx = {e^[(x+3)ln(x+1)]}×[ln(x+1)+(x+3)/(x+1)]
= [(x+1)^(x+3)]×[ln(x+1)+(x+3)/(x+1)]