原式等于
1²-2²+3²-4²+。。。-100²+101²
=(1-2)*(1+2)+(3-4)*(3+4)+。。。+(99-100)*(99+100)+101²
=-(1+2+3+。。。+100)+101²
=-(101*100/2)+101²
=101*101-101*50
=101*51
=5151
平方差
原式=(101²-100²)+(99²-98²)+……+(3²-2²)+1²
=(101+100)(101-100)+(99+98)(99-98)+……+(3+2)(3-2)+1
=(101+100)×1+(99+98)×1+……+(3+2)×1+1
=101+100+99+98+……+3+2+1
=101+(100+1)+(99+2)+……+(51+50)
=101+51
=5151