Question

Tính B=(1/1009+1/1010+...+1/2016)/(1-1/2+1/3-1/4...-1/2016) Ai làm đc thì mk công nhận là giỏi

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Answer 1

xét mẫu

(1-1/2+1/3-1/4....-1/2016)=(1+1/2-1+1/3+1/4-2/4+1/5+1/6-2/6+......+1/2016-2/2016)

(1-1/2+1/3-1/4+.....-1/2016)=(1+1/2-1+1/3+1/4-1/2+1/5+1/6-1/3+......+1/2016-1/1008)

(1-1/2+1/3-1/4+.....-1/2016)=(1-1+1/2-1/2+1/3-1/3+......+1/1008-1/1008)+(1/1009+1/1010+....+1/2016)

=>(1-1/2+1/3-1/4+....-1/2016)=1/1009+1/1010+....+1/2016

=>B=1

nha