2+4+6.+(2n+2)=

2+4+6.+(2n+2)=
2+4+6.+(2n+2)=

2+4+6.+(2n+2)=
(n+2)(n+1)
自己检验下哦
晕,楼上动作快,你叼

=2(1+2+3+...+n+1)
=2*(n+1)(n+2)/2
=(n+1)(n+2)
=n^2+3n+2

这是一个等差数列，公式是[首+尾]数量/2，所以原式=[（2+2n+2）（2n+2）/2]/2=(n+2)(n+1)

(n+2)n

=((2+2n+2)*(n+1))/2
=2(n+2)*(n+1)/2
=(n+2)(n+1)
=n^2+n+2n+2
=n^2+3n+2