计算:12-22+32-42+…+992-1002=_.

问题描述:

计算:12-22+32-42+…+992-1002=______.

原式=(12-22)+(32-42)+…+(992-1002
=(1-2)(1+2)+(3-4)(3+4)+…+(99-100)(99+100)
=-(1+2)-(3+4)-…-(99+100)
=-(1+2+3+4+…+99+100)
=-5050.
故本题答案为:-5050.