已知a与-1的差为2,b是-2的相反数,试求代数式1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2010)(b+2010)值
问题描述:
已知a与-1的差为2,b是-2的相反数,试求代数式1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2010)(b+2010)值
答
a与-1的差为2
a-(-1)=2
a=1
b是-2
b+(-2)=0
b=2
1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2010)(b+2010)
=1/1*2+1/2*3+1/3*4+1/4*5+.........+1/2011*2012
=1-1/2+1/2-1/3+1/3-1/4+.........+1/2011-1/2012
=1-1/2012
=2011/2012 ...
答
a与-1的差为2,b是-2的相反数
a-(-1)=2.b=-(-2)
a=1,b=2
∴1/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2010)(b+2010)
=1/1x2+1/2x3+1/3x4+……+1/2011x2012
=1-1/2+1/2-1/3+1/3-1/4+……+1/2011-1/2012
=1-1/2012
=2011/2012
答
a与-1的差为2a-(-1)=2a=1b是-2的相反数b+(-2)=0b=21/ab+1/(a+1)(b+1)+1/(a+2)(b+2)+...+1/(a+2010)(b+2010)=1/1*2+1/2*3+1/3*4+1/4*5+.+1/2011*2012=1-1/2+1/2-1/3+1/3-1/4+.+1/2011-1/2012=1-1/2012=2011/2012...