Question

观察下列各式二等于一乘二二加四等于六等于二乘三二加四加六等于十二等于三乘

Answer 1

2=1x2

2+4=6=2x3

2+4+6=12=3x4

2+4+6+8=20=4x5

.

2+4+6+8+...+2n=n(n+1)