Question

1. Ta có thể viết số hữu tỉ \(\frac{-5}{16}\) dưới các dạng sau đây :

a) \(\frac{-5}{16}\) là tích của hai số hữu tỉ. Ví dụ : \(\frac{-5}{16}\) = \(\frac{-5}{2}\).\(\frac{1}{8}\)

b) \(\frac{-5}{16}\) là thương của hai số hữu tỉ. Ví dụ: \(\frac{-5}{16}\) = \(\frac{-5}{2}\):8

2. Tính:

a) \(\frac{-3}{4}.\frac{12}{-5}.\)\(\left(-\frac{25}{6}\right)\)

b) (\(-2\)).\(\frac{-38}{21}.\frac{-7}{4}.\left(-\frac{3}{8}\right)\)

c) \(\left(\frac{11}{12}:\frac{33}{16}\right).\frac{3}{5}\)

d) \(\frac{7}{23}.\left[\left(-\frac{8}{6}\right)-\frac{45}{18}\right]\)

3. Tính:

a) \(\left(\frac{-2}{3}+\frac{3}{7}\right):\frac{4}{5}+\left(\frac{-1}{3}+\frac{4}{7}\right):\frac{4}{5}\)

b) \(\frac{5}{9}:\left(\frac{1}{11}-\frac{5}{22}\right)+\frac{5}{9}:\left(\frac{1}{15}-\frac{2}{3}\right)\)

Answer 1

3,

a) $\left(\frac{-2}{3}+\frac{3}{7}\right):\frac{4}{5}+\left(\frac{-1}{3}+\frac{4}{7}\right):\frac{4}{5}$

= \(-\frac{5}{21}:\frac{4}{5}+\frac{5}{21}:\frac{4}{5}\)

= \(\left(-\frac{5}{21}+\frac{5}{21}\right):\frac{4}{5}\)

= \(0:\frac{4}{5}=0\)

Answer 2

2,

a) \(\frac{-3}{4}\))

= \(\frac{-3.4.3.\left(-5\right).5}{4.\left(-5\right).3.3}\)

= \(-5\)

b) ().\(\frac{-38}{21}\)

= \(\frac{19}{8}\)

c)

= \(\left(\frac{11}{12}.\frac{16}{33}\right).\frac{3}{5}\)

= \(\frac{4}{9}.\frac{3}{5}\)

= \(\frac{4}{15}\)

d) \(\frac{7}{23}\left[\left(\frac{-8}{6}\right)-\frac{45}{18}\right]\)

= \(\frac{7}{23}.\left(\frac{-41}{10}\right)\)

= \(\frac{-287}{203}\)

3. Tính:

a)

\(+\)\(\frac{-1}{3}+\frac{4}{7}\)) : \(\frac{4}{5}\)

= 0 : \(\frac{4}{5}\)

= 0

b) \(\frac{5}{9}\)\(\frac{5}{9}\)

: \(\frac{-3}{22}\)+ \(\frac{5}{9}\): \(\frac{-3}{5}\)

= \(\frac{5}{9}\): \(\frac{-81}{110}\)

= \(\frac{-550}{729}\)

Answer 3

https://vietjack.com/giai-toan-lop-7/

Answer 4

1.

Mỗi câu có nhiều đáp án, chẳng hạn:

a) \(-\frac{5}{16}=\left(-\frac{5}{4}\right).\frac{1}{4}=\left(-\frac{5}{8}\right).\frac{1}{2}=\left(-\frac{10}{2}\right).\frac{1}{16}.\)

b) \(-\frac{5}{16}=\left(-\frac{5}{8}\right):2=\left(-\frac{5}{4}\right):4.\)

Chúc bạn học tốt!