1^2-2^2+3^2-4^2+...+99^2-100^2+101^2
=(1+2)(1-2)+(3-4)(3+4)+...+(99+100)(99-100)+101^2 [平方差公式:a^2-b^2=(a+b)(a-b)]
=(-1)[3+7+11+...+199]+101^2 (将-1提出来)
=(-1)*[(3+199)*50]/2+101^2 (3+7+11+...+199是以首项a1为3,公差为4的等差数列,到a50=199项共50项,按等差数列求和公式:S=(a1+an)*n/2 (n为项数)]
=-5050+10201
=5151