計算:12-22+32-42+52-62+…+20072-20082=________.
-2017036
分析:根據(jù)平方差公式(a+b)(a-b)=a
2-b
2,即可求出答案.
解答:1
2-2
2+3
2-4
2+5
2-6
2+…+2005
2-2006
2+2007
2-2008
2=-[(2
2-1
2)+(4
2-3
2)+(6
2-5
2)+…+(2006
2-2005
2)+(2008
2-2007
2)],
利用平方差公式1
2-2
2+3
2-4
2+5
2-6
2+…+2005
2-2006
2+2007
2-2008
2=-[(=-[(2
2-1
2)+(4
2-3
2)+(6
2-5
2)+…+(2006
2-2005
2)+(2008
2-2007
2)]
=-[(2-1)(2+1)+(4-3)(4+3)+(6-5)(6+5)+…+(2006-2005)(2006+2005)+(2008-2007)(2008+2007)]
=-(1+2+3+4+…+2006+2007+2008=-
=-2 017036.
故答案為:-2 017036.
點評:本題考查了平方差公式,難度不大,關鍵是找出題目的規(guī)律再進行解答.