Đại số lớp 6

LN

a,2/3x-3/2x=5/12

b,2/5+3/5×(3x-3×7)=-53/10

c,7/9:(2+3/4x)+5/3=23/27

d,-2/3×x+1/5=3/10

e,|x|-3/4=5/3

Giúp em với ạ

NQ
2 tháng 5 2017 lúc 20:56

a) \(\dfrac{2}{3}x-\dfrac{3}{2}x=\dfrac{5}{12}\)

\(x\left(\dfrac{2}{3}-\dfrac{3}{2}\right)=\dfrac{5}{12}\)

\(x\cdot\left(-\dfrac{5}{6}\right)=\dfrac{5}{12}\)

\(x=\dfrac{5}{12}:\left(-\dfrac{5}{6}\right)\)

\(x=-\dfrac{1}{2}\)

Vậy \(x=-\dfrac{1}{2}\).

b) \(\dfrac{2}{5}+\dfrac{3}{5}\cdot\left(3x-3\cdot7\right)=-\dfrac{53}{10}\)

\(\dfrac{3}{5}\left(3x-3\cdot7\right)=-\dfrac{53}{10}-\dfrac{2}{5}\)

\(\dfrac{3}{5}\left(3x-3\cdot7\right)=-\dfrac{57}{10}\)

\(3x-3\cdot7=-\dfrac{57}{10}:\dfrac{3}{5}\)

\(3x-3\cdot7=-\dfrac{19}{2}\)

\(3x-21=-\dfrac{19}{2}\)

\(3x=-\dfrac{19}{2}+21\)

\(3x=\dfrac{23}{2}\)

\(x=\)\(\dfrac{23}{2}:3\)

\(x=\dfrac{23}{6}\)

Vậy \(x=\dfrac{23}{6}\).

c) \(\dfrac{7}{9}:\left(2+\dfrac{3}{4x}\right)+\dfrac{5}{3}=\dfrac{23}{27}\)

\(\dfrac{7}{9}:\left(2+\dfrac{3}{4x}\right)=\dfrac{23}{27}-\dfrac{5}{3}\)

\(\dfrac{7}{9}:\left(2+\dfrac{3}{4x}\right)=-\dfrac{22}{27}\)

\(2+\dfrac{3}{4x}=\dfrac{7}{9}:-\dfrac{22}{27}\)

\(2+\dfrac{3}{4x}=-\dfrac{21}{22}\)

\(\dfrac{3}{4x}=-\dfrac{21}{22}-2\)

\(\dfrac{3}{4x}=-\dfrac{65}{22}\)

\(4x=\dfrac{3\cdot22}{-65}\)

\(4x=-\dfrac{66}{65}\)

\(x=-\dfrac{66}{65}:4\)

\(x=-\dfrac{33}{130}\)

Vậy \(x=-\dfrac{33}{130}\).

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

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

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

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

\(x=-\dfrac{3}{20}\)

Vậy \(x=-\dfrac{3}{20}\).

e) \(\left|x\right|-\dfrac{3}{4}=\dfrac{5}{3}\)

\(\left|x\right|=\dfrac{5}{3}+\dfrac{3}{4}\)

\(\left|x\right|=\dfrac{29}{12}\)

\(x=\dfrac{29}{12}\) hoặc \(=-\dfrac{29}{12}\)

Vậy \(x\in\left\{\dfrac{29}{12};-\dfrac{29}{12}\right\}\).

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