Question

研究下列算式：4x1x2=3^2-1,4x2x3=5^2-1,4x2x4=7^2-1,4x4x5=9^2-1,4x5x6

Answer 1

4x1x2=3^2-1,

4x2x3=5^2-1,

4x3x4=7^2-1,

4x4x5=9^2-1,

4x5x6=11^2-1,

……

4xNx(N+1)=(N+N+1)^2-1

如4x99x100=(99+100)^2-1=39600