Question

A=\(\frac{-3}{5}+\left(\frac{-2}{5}+2\right)\)

\(B=\left(6-2\frac{4}{5}\right)\times3\frac{1}{8}-1\frac{3}{5}=\frac{1}{4}\)

Tính nhanh

\(A=\frac{5}{1\times7}+\frac{5}{4\times7}+\frac{5}{7\times10}+......+\frac{5}{101\times104}\)

Answer 1

A và B dễ 

Bài 2:

sai đề bài vì ngay từ cái phép tính đầu đã ko theo quy luật rồi 

Answer 2

\(A=\frac{-3}{5}-\frac{2}{5}+2\)

\(A=-1+2=1\)

\(B=\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}=\frac{1}{4}\)

nÀ NÍ sao lại = đây là dấu trừ hay cộng 1/4

Answer 3

;1/4 nha

Answer 4

\(B=\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\)

\(B=\frac{16}{5}.\frac{25}{8}-\frac{32}{5}\)

\(B=10-\frac{32}{5}=\frac{18}{5}\)

Answer 5

\(B=\left(6-2\frac{4}{5}\right)\times3\frac{1}{8}-1\frac{3}{5}\div\frac{1}{4}\)

Answer 6

\(A=-\frac{3}{5}+\left(-\frac{2}{5}+2\right).\)

\(A=-\frac{3}{5}+-\frac{2}{5}+2\)

\(A=\left(-1\right)+2=1\)

\(B=\left(6-2\frac{4}{5}\right).3\frac{1}{8}-1\frac{3}{5}:\frac{1}{4}\)

\(B=\left(6-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\)

\(B=\left(\frac{30}{5}-\frac{14}{5}\right).\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\)

\(B=\frac{16}{5}.\frac{25}{8}-\frac{8}{5}:\frac{1}{4}\)

\(B=\frac{400}{40}-\frac{32}{5}\)

\(B=10-\frac{32}{5}=\frac{18}{5}\)

Answer 7

\(A=\frac{5}{1\cdot7}+\frac{5}{4\cdot7}+\frac{5}{7\cdot10}+...+\frac{5}{101\cdot104}\)

\(A=5\left(\frac{1}{1\cdot7}+\frac{1}{4\cdot7}+\frac{1}{7\cdot10}+...+\frac{1}{101\cdot104}\right)\)

\(A=5\left(1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+\frac{1}{10}-...-\frac{1}{101}+\frac{1}{101}-\frac{1}{104}\right)\)

\(A=5\left(1-\frac{1}{104}\right)\)

\(A=5.\frac{103}{104}=\frac{515}{104}\)