Question

\(T\text{Í}NH:a,\frac{3}{8\times11}+\frac{3}{11\times14}+\frac{3}{14\times17}+\frac{3}{17\times10}\)

\(b,\frac{6}{13\times19}+\frac{6}{19\times25}+...+\frac{6}{613\times619}\)

Answer 1

A = 3 / 8 x 11 + 3 / 11 x 14 + 3 / 14 x 17 + 3 / 17 x 10

A = 1 / 8 - 1 / 11 +  1 / 11 - 1 / 14 + 1 / 14 - 1 / 17 + 1 / 17 - 1 / 10

A = 1 / 8 - 1 / 10

A = 1 / 40

B = 6 / 13 x 19 + 6 / 19 x 25 + ... + 6 / 613 x 619

B = 1 / 13 - 1 / 19 + 1 / 19 - 1 / 25 + ... + 1 / 613 - 1 / 619

B = 1 / 13 - 1 / 619 

B = 606 / 8047

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Answer 2

phần a phân số cuối có mẫu sai hay sao ý
 

Answer 3

A = 3 / 8 x 11 + 3 / 11 x 14 + 3 / 14 x 17 + 3 / 17 x 10

A = 1 / 8 - 1 / 11 +  1 / 11 - 1 / 14 + 1 / 14 - 1 / 17 + 1 / 17 - 1 / 10

A = 1 / 8 - 1 / 10

A = 1 / 40

B = 6 / 13 x 19 + 6 / 19 x 25 + ... + 6 / 613 x 619

B = 1 / 13 - 1 / 19 + 1 / 19 - 1 / 25 + ... + 1 / 613 - 1 / 619

B = 1 / 13 - 1 / 619 

B = 606 / 8047