Giải bài 1.31 trang 24

Đề bài

Tìm x, biết:

$\begin{array}{c}a)2x+\frac{1}{2}=\frac{7}{9}\\ b)\frac{3}{4}-6x=\frac{7}{13}\end{array}$

Lời giải chi tiết

$\begin{array}{c}a)2x+\frac{1}{2}=\frac{7}{9}\\ 2x=\frac{7}{9}-\frac{1}{2}\\ 2x=\frac{14}{18}-\frac{9}{18}\\ 2x=\frac{5}{18}\\ x=\frac{5}{18}:2\\ x=\frac{5}{18}.\frac{1}{2}\\ x=\frac{5}{36}\end{array}$

Vậy $x=\frac{5}{36}$

$\begin{array}{c}b)\frac{3}{4}-6x=\frac{7}{13}\\ 6x=\frac{3}{4}-\frac{7}{13}\\ 6x=\frac{39}{52}-\frac{28}{52}\\ 6x=\frac{11}{52}\\ x=\frac{11}{52}:6\\ x=\frac{11}{52}.\frac{1}{6}\\ x=\frac{11}{312}\end{array}$

Vậy $x=\frac{11}{312}$