Question

[Vũ Khánh Hien]

A, 1/1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4.

B, 4/7 nhân 8/9 + 4/7 nhân  1/9.

C, 13/6 nhân 3/8 - 3/8 nhân 7/6.

D, 1/1 nhân 2 + 1/2 nhân 3 + 1/3 nhân 4 +........ + 1/9 nhân 10.

Ai đúng mình like cho nhé !

Answer 1

[Vũ Khánh Hien]

À quên mọi người tính nhanh nhé !

Answer 2

[I don't need you]

a) \(\frac{1}{1}-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}\)

\(=1-\frac{1}{4}\)

\(=\frac{3}{4}\)

b) \(\frac{4}{7}\times\frac{8}{9}+\frac{4}{7}\times\frac{1}{9}\)

\(=\frac{4}{7}\times\left(\frac{8}{9}+\frac{1}{9}\right)\)

\(=\frac{4}{7}\times1\)

\(=\frac{4}{7}\)

c) \(\frac{13}{6}\times\frac{3}{8}-\frac{3}{8}\times\frac{7}{6}\)

\(=\frac{3}{8}\times\left(\frac{13}{6}-\frac{7}{6}\right)\)

\(=\frac{3}{8}\times1\)

\(=\frac{3}{8}\)

d) \(\frac{1}{1x2}+\frac{1}{2x3}+\frac{1}{3x4}+...+\frac{1}{9x10}\)

\(=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\)

\(=1-\frac{1}{10}\)

\(=\frac{9}{10}\)