Ôn tập toán 6

Hoàng Thúy An

a\(\dfrac{5}{6}x-\dfrac{2}{3}=3\dfrac{1}{2}\)

b\(\dfrac{4}{5}-\dfrac{3}{4}\div x=0,3\)

c\(\dfrac{-3}{2}-\dfrac{1}{4}x=1\dfrac{1}{3}-0,2x\)

d\(\left|\dfrac{3}{5}x+\dfrac{4}{3}\right|:\dfrac{2}{3}-0,5=1\dfrac{1}{2}\)

e\(\dfrac{4x-5}{2-3x}=\dfrac{3}{4}\)

giúp mình nhé

b) \(\dfrac{4}{5}-\dfrac{3}{4}:x=0,3\)

\(\Rightarrow0,8-0,75:x=0,3\)

\(\Rightarrow0,75:x=0,5\)

\(\Rightarrow x=1,5\)

c) \(\dfrac{-3}{2}-\dfrac{1}{4}x=1\dfrac{1}{3}-0,2x\)

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

\(\Rightarrow x=\dfrac{-17}{6}\cdot20\)

\(\Rightarrow x=\dfrac{-170}{3}\)

d) \(\left|\dfrac{3}{5}x+\dfrac{4}{3}\right|:\dfrac{2}{3}-0,5=1\dfrac{1}{2}\)

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

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

\(\Rightarrow\left[{}\begin{matrix}\dfrac{3}{5}x+\dfrac{4}{3}=\dfrac{4}{3}\Rightarrow x=0\\\dfrac{3}{5}x+\dfrac{4}{3}=-\dfrac{4}{3}\Rightarrow x=\dfrac{-40}{9}\end{matrix}\right.\)

e) \(\dfrac{4x-5}{2-3x}=\dfrac{3}{4}\)

\(\Rightarrow4\left(4x-5\right)=3\left(2-3x\right)\)

\(\Rightarrow16x-20=6-9x\)

\(\Rightarrow16x+9x=20+6\)

\(\Rightarrow25x=26\)

\(x=\dfrac{26}{25}\)

Khánh Linh
21 tháng 8 2017 lúc 16:29

a, \(\dfrac{5}{6}x-\dfrac{2}{3}=3\dfrac{1}{2}\)

<=> \(\dfrac{5}{6}x-\dfrac{2}{3}=\dfrac{7}{2}\)

<=> \(\dfrac{5}{6}x=\dfrac{25}{6}\)

<=> x = 5
@hoang thuy an

Khánh Linh
21 tháng 8 2017 lúc 16:31

b, \(\dfrac{4}{5}-\dfrac{3}{4}:x=0,3\)

<=> \(\dfrac{4}{5}-\dfrac{3}{4}:x=\dfrac{3}{10}\)

<=> \(\dfrac{3}{4}:x=\dfrac{1}{2}\)

<=> x = \(\dfrac{3}{2}\)

@hoang thuy an

Khánh Linh
21 tháng 8 2017 lúc 16:34

c, -\(\dfrac{3}{2}-\dfrac{1}{4}x=1\dfrac{1}{3}-0,2x\)

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

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

<=> -\(\dfrac{1}{20}x=\dfrac{17}{6}\)

<=> x = -\(\dfrac{170}{3}\)

@hoang thuy an

Khánh Linh
21 tháng 8 2017 lúc 16:38

d, |\(\dfrac{3}{5}x+\dfrac{4}{3}\)| : \(\dfrac{2}{3}-0,5=1\dfrac{1}{2}\)

<=> |\(\dfrac{3}{5}x+\dfrac{4}{3}\)| : \(\dfrac{2}{3}-\dfrac{1}{2}=\dfrac{3}{2}\)

<=> |\(\dfrac{3}{5}x+\dfrac{4}{3}\)| : \(\dfrac{2}{3}=2\)

<=> |\(\dfrac{3}{5}x+\dfrac{4}{3}\)| = \(\dfrac{4}{3}\)

<=> \(\left\{{}\begin{matrix}\dfrac{3}{5}x+\dfrac{4}{3}=\dfrac{4}{3}\\\dfrac{3}{5}x+\dfrac{4}{3}=-\dfrac{4}{3}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}\dfrac{3}{5}x=0\\\dfrac{3}{5}x=-\dfrac{8}{3}\end{matrix}\right.\)\(\Leftrightarrow\left\{{}\begin{matrix}x=0\\x=-\dfrac{40}{9}\end{matrix}\right.\)

@hoang thuy an

Khánh Linh
21 tháng 8 2017 lúc 16:40

e, \(\dfrac{4x-5}{2-3x}=\dfrac{3}{4}\)

<=> 4(4x - 5) = 3(2 - 3x)
<=> 16x - 20 = 6 - 9x
<=> 16x + 9x = 6 + 20
<=> 25x = 26
<=> x = \(\dfrac{26}{25}\)
@hoang thuy an

a) \(\dfrac{5}{6}x-\dfrac{2}{3}=3\dfrac{1}{2}\)

\(\Rightarrow\dfrac{5}{6}x=\dfrac{7}{2}+\dfrac{2}{3}\)

\(\Rightarrow x=\dfrac{25}{6}\cdot\dfrac{6}{5}\)

\(\Rightarrow x=5\)


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