Question

ChoA=\(1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}....+\frac{1}{49}-\frac{1}{50}\)

B=\(\frac{1}{25}+\frac{1}{26}+\frac{1}{27}.....+\frac{1}{50}\)

Chứng tỏ rằng A=B

Answer 1

\(A=1-\frac{1}{2}+\frac{1}{3}-\frac{1}{4}+....+\frac{1}{49}-\frac{1}{50}=\left(1+\frac{1}{3}+\frac{1}{5}+....+\frac{1}{49}\right)-\left(\frac{1}{2}+\frac{1}{4}+....+\frac{1}{50}\right)=\left(1+\frac{1}{2}+\frac{1}{3}+....+\frac{1}{50}\right)-2\left(\frac{1}{2}+\frac{1}{4}+....+\frac{1}{50}\right)=\left(1+\frac{1}{2}+\frac{1}{3}+....+\frac{1}{50}\right)-\left(1+\frac{1}{2}+...+\frac{1}{25}\right)=\frac{1}{26}+\frac{1}{27}+....+\frac{1}{50}\Rightarrow A=B\text{(đpcm)}\)

Answer 2

Ta cos ..............

suy ra A=B

Answer 3

bài này chắc mình không làm được rồi, xin lỗihihi