Question

[Ng Minh Thư]

Giúp tớ bài 5 vs ạ, tớ cảm ơn

Answer 1

[Nguyễn Lê Phước Thịnh]

Bài 5:

1: \(\dfrac{2}{5}+\dfrac{3}{5}x=\dfrac{9}{20}\)

=>\(\dfrac{3}{5}x=\dfrac{9}{20}-\dfrac{2}{5}=\dfrac{9}{20}-\dfrac{8}{10}=\dfrac{1}{10}\)

=>\(x=\dfrac{1}{10}:\dfrac{3}{5}=\dfrac{1}{10}\cdot\dfrac{5}{3}=\dfrac{5}{30}=\dfrac{1}{6}\)

2: \(\dfrac{1}{4}+\dfrac{1}{3}:\left(3x\right)=-5\)

=>\(\dfrac{1}{3}:\left(3x\right)=-5-\dfrac{1}{4}=-\dfrac{21}{4}\)

=>\(3x=-\dfrac{1}{3}:\dfrac{21}{4}=-\dfrac{1}{3}\cdot\dfrac{4}{21}=-\dfrac{4}{63}\)

=>\(x=-\dfrac{4}{63}:3=-\dfrac{4}{189}\)

3: \(-\dfrac{21}{13}x+\dfrac{1}{3}=-\dfrac{2}{3}\)

=>\(-\dfrac{21}{13}x=-\dfrac{2}{3}-\dfrac{1}{3}=-\dfrac{3}{3}=-1\)

=>\(x=1:\dfrac{21}{13}=\dfrac{13}{21}\)

4: \(\dfrac{3}{4}x-\dfrac{1}{2}=\dfrac{3}{7}\)

=>\(\dfrac{3}{4}x=\dfrac{1}{2}+\dfrac{3}{7}=\dfrac{7+6}{14}=\dfrac{13}{14}\)

=>\(x=\dfrac{13}{14}:\dfrac{3}{4}=\dfrac{13}{14}\cdot\dfrac{4}{3}=\dfrac{52}{42}=\dfrac{26}{21}\)

5: \(\dfrac{2}{3}x+\dfrac{1}{2}=\dfrac{3}{10}-\dfrac{1}{5}\)

=>\(\dfrac{2}{3}x+\dfrac{1}{2}=\dfrac{1}{10}\)

=>\(\dfrac{2}{3}x=\dfrac{1}{10}-\dfrac{1}{2}=\dfrac{1}{10}-\dfrac{5}{10}=-\dfrac{4}{10}=-\dfrac{2}{5}\)

=>\(x=-\dfrac{2}{5}:\dfrac{2}{3}=-\dfrac{2}{5}\cdot\dfrac{3}{2}=-\dfrac{3}{5}\)

6: \(\dfrac{2}{3}+\dfrac{1}{3}x=-\dfrac{1}{2}\)

=>\(\dfrac{1}{3}x=-\dfrac{1}{2}-\dfrac{2}{3}=\dfrac{-7}{6}\)

=>\(x=-\dfrac{7}{6}:\dfrac{1}{3}=-\dfrac{7}{6}\cdot3=-\dfrac{7}{2}\)

7: \(\dfrac{11}{12}x+\dfrac{3}{4}=-\dfrac{1}{6}\)

=>\(\dfrac{11}{12}x=-\dfrac{1}{6}-\dfrac{3}{4}=\dfrac{-2}{12}-\dfrac{9}{12}=-\dfrac{11}{12}\)

=>x=-1

8: \(-\dfrac{5}{6}-\dfrac{2}{3}x=\dfrac{7}{12}+\dfrac{-1}{3}\)

=>\(-\dfrac{5}{6}-\dfrac{2}{3}x=\dfrac{7}{12}-\dfrac{4}{12}=\dfrac{3}{12}=\dfrac{1}{4}\)

=>\(\dfrac{2}{3}x=-\dfrac{5}{6}-\dfrac{1}{4}=\dfrac{-10}{12}-\dfrac{3}{12}=-\dfrac{13}{12}\)

=>\(x=-\dfrac{13}{12}:\dfrac{2}{3}=-\dfrac{13}{12}\cdot\dfrac{3}{2}=\dfrac{-39}{24}=\dfrac{-13}{8}\)

9: \(2\dfrac{2}{3}x+8\dfrac{2}{3}=3\dfrac{1}{3}\)

=>\(\dfrac{8}{3}x=3+\dfrac{1}{3}-8-\dfrac{2}{3}=-5-\dfrac{1}{3}=-\dfrac{16}{3}\)

=>\(x=-\dfrac{16}{3}:\dfrac{8}{3}=-\dfrac{16}{3}\cdot\dfrac{3}{8}=-\dfrac{16}{8}=-2\)

10: \(\dfrac{3}{4}-\dfrac{1}{4}:\left(x:\dfrac{5}{2}\right)=-3\)

=>\(\dfrac{1}{4}:\left(x:\dfrac{5}{2}\right)=\dfrac{3}{4}+3=\dfrac{15}{4}\)

=>\(x:\dfrac{5}{2}=\dfrac{1}{4}:\dfrac{15}{4}=\dfrac{1}{15}\)

=>\(x=\dfrac{1}{15}\cdot\dfrac{5}{2}=\dfrac{1}{6}\)