第11题解题过程(简便计算)
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(10)原式=1/2×(1/1x2-1/2x3+1/2x3-1/3x4+1/3x4-1/x45+……+1/20x21-1/21x22)
=1/2x(1/1x2-1/21x22)
=1/2x(1/2-1/462)
=1/2x230/462
=115/462
(11)原式=1/2+(1/3+2/3)+(1/4+2/4+3/4)+……+(1/100+2/100+……+99/100)
=1/2+2/2+3/2+……+99/2
=(1/2+99/2)×99÷2
=50×99÷2
=2475
=1/2x(1/1x2-1/21x22)
=1/2x(1/2-1/462)
=1/2x230/462
=115/462
(11)原式=1/2+(1/3+2/3)+(1/4+2/4+3/4)+……+(1/100+2/100+……+99/100)
=1/2+2/2+3/2+……+99/2
=(1/2+99/2)×99÷2
=50×99÷2
=2475
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