Giải bài 4 trang 32

Đề bài

Tìm x biết:

a) $1\frac{5}{6}+x=\frac{7}{3}$

b) $x-\frac{3}{-2}=3\frac{4}{5}$

c) $x:\frac{3}{-5}=3\frac{1}{2}$

d) $2\frac{1}{6}.x=\frac{-2}{5}$

Lời giải chi tiết

a)

 $\begin{array}{c}1\frac{5}{6}+x=\frac{7}{3}\\ x=\frac{7}{3}-1\frac{5}{6}\\ x=\frac{7}{3}-\frac{11}{6}\\ x=\frac{14}{6}-\frac{11}{6}\\ x=\frac{3}{6}=\frac{1}{2}\end{array}$

b)

 $\begin{array}{c}x=3\frac{4}{5}+\frac{3}{-2}\\ x=\frac{19}{5}+\frac{3}{-2}\\ x=\frac{38}{10}+\frac{-15}{10}\\ x=\frac{23}{10}\end{array}$

c)

 $\begin{array}{c}x:\frac{3}{-5}=3\frac{1}{2}\\ x=3\frac{1}{2}.\frac{3}{-5}\\ x=\frac{7}{2}.\frac{3}{-5}\\ x=\frac{-21}{10}\end{array}$

d)

 $\begin{array}{c}2\frac{1}{6}.x=\frac{-2}{5}\\ x=\frac{-2}{5}:2\frac{1}{6}\\ x=\frac{-2}{5}:\frac{13}{6}\\ x=\frac{-2}{5}.\frac{6}{13}\\ x=\frac{-12}{65}\end{array}$