Question

已知两公式：1×1+2×2+……+n×n=n×(n+1) ×(2×n+1)÷6；（n+1）×（n-1）=n×n-1,请你

Answer 1

1*3+3*5+5*7+...+99*101

=(2-1)*(2+1)+(4-1)*(4+1)+...(100-1)*(100+1)

=(2*2+4*4+...100*100)-1*50

=4*(1*1+2*2+...50*50)-50

=4*(50+1)*50*(100+1)/6-50

=171650