Question

[hoa HOA]

\(\frac{4}{7x31}+\frac{6}{7x41}+\frac{9}{10x41}+\frac{7}{10x57}\)

Answer 1

[ST]

Đặt A là tên của biểu thức

\(A=\frac{4}{7.31}+\frac{6}{7.41}+\frac{9}{10.41}+\frac{7}{10.57}\)

\(=\frac{20}{31.35}+\frac{30}{35.41}+\frac{45}{41.50}+\frac{35}{50.57}\)

\(=5\left(\frac{4}{31.35}+\frac{6}{35.41}+\frac{9}{41.50}+\frac{7}{50.57}\right)\)

\(=5\left(\frac{1}{31}-\frac{1}{35}+\frac{1}{35}-\frac{1}{41}+\frac{1}{41}-\frac{1}{50}+\frac{1}{50}-\frac{1}{57}\right)\)

\(=5\left(\frac{1}{31}-\frac{1}{57}\right)=5\cdot\frac{26}{1767}=\frac{130}{1767}\)

Answer 2

[Trương Cẩm Vân]

130/1767