x的3n+1次方×x+3x的n+一次方×x的2n+1次方=几

问题描述:

x的3n+1次方×x+3x的n+一次方×x的2n+1次方=几

=x^(3n+1+1)+3x^(n+1+2n+1)
=x^(3n+2)+3x^(3n+2)
=4x^(3n+2)