已知有理数a、b满足▕ab-2▏+(1-a)²=0
问题描述:
已知有理数a、b满足▕ab-2▏+(1-a)²=0
求1÷ab+1÷[(a+1)×(b+1)]+1÷[(a+2)×(b=2)]+...+1÷[(a+2010)×(b+2010)]的值.
答
2011/2012!
已知有理数a、b满足▕ab-2▏+(1-a)²=0
求1÷ab+1÷[(a+1)×(b+1)]+1÷[(a+2)×(b=2)]+...+1÷[(a+2010)×(b+2010)]的值.
由a、b满足▕ab-2▏+(1-a)²=0可得a=1,b=2
所以,1÷ab+1÷[(a+1)×(b+1)]+1÷[(a+2)×(b=2)]+...+1÷[(a+2010)×(b+2010)]
等于1/(1*2)+1/(2*3)+1/(3*4)+……+1/(2011*2012)
=(2-1)/(1*2)+(3-2)/(2*3)+(4-3)/(3*4)+……+(2012-2011)/(2011*2012)
=(1/1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/2011-1/2012)
=1/1+(-1/2+1/2)+(-1/3+1/3)-1/4+……+1/2011-1/2012
=1/1-1/2012
=2011/2012