x的3n次方×x+3x的n+一次方×x的2n+1次方=几

x^3n*x+3x^(n+1)*x^(2n+1)
=x^(3n+1)+3*x^(2n+2)
=x^(3n+1)*(1+3x)
再问： 问题补充！！！
再答： x^(3n+1)*x+3x^(n+1)*x^(2n+1) 是这样吗？ =x^(3n+2)+3*x^(3n+2) =4*x^(3n+2)