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

<=> \(\dfrac{-18}{12}+\dfrac{12x}{12}-\dfrac{15}{12}=\dfrac{-4}{12}-\dfrac{24x}{12}\)

<=> -18 + 12x - 15 = -4 - 24x

<=> 12x + 24x = 18 + 15 - 4

<=> 36x = 29

<=> x = \(\dfrac{29}{36}\)

6. \(\dfrac{3}{4}x-\dfrac{3}{2}=\dfrac{5}{6}+\dfrac{3}{8}x\)

<=> \(\dfrac{18x}{24}-\dfrac{36}{24}=\dfrac{20}{24}+\dfrac{9x}{24}\)

<=> 18x - 36 = 20 + 9x

<=> 18x - 9x = 20 + 36

<=> 9x = 56

<=> x = \(\dfrac{56}{9}\)

7. \(3-\left(\dfrac{1}{2}+2x\right)=\dfrac{2}{3}-x\)

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

<=> \(\dfrac{18}{6}-\dfrac{3}{6}-\dfrac{12x}{6}=\dfrac{4}{6}-\dfrac{6x}{6}\)

<=> 18 - 3 - 12x = 4 - 6x

<=> 15 - 4 = 12x - 6x

<=> 11 = 6x

<=> x = \(\dfrac{11}{6}\)

2/ \(\dfrac{1}{7}.\dfrac{1}{3}+\dfrac{1}{7}.\dfrac{1}{2}-\dfrac{1}{7}\)

= \(\dfrac{1}{7}\left(\dfrac{1}{3}+\dfrac{1}{2}-1\right)\)

= \(\dfrac{1}{7}\left(\dfrac{2}{6}+\dfrac{3}{6}-\dfrac{6}{6}\right)\)

= \(\dfrac{1}{7}.\dfrac{-1}{6}\)

= \(\dfrac{1.\left(-1\right)}{7.6}\)

= \(\dfrac{-1}{42}\)

\(\sqrt{x-2}-\sqrt{9x-18}+4=0\)             ĐKXĐ: \(x\ge2\)

<=> \(\sqrt{x-2}=\sqrt{9x-18}-4\)

<=> \(x-2=\left(\sqrt{9x-18}-4\right)^2\)

<=> \(x-2=\left(9x-18\right)-8\sqrt{9x-18}+16\)

<=> \(x-2-9x+18-16=-8\sqrt{9x-18}\)

<=> \(-8x=-8\sqrt{9x-18}\)

<=> \(\sqrt{9x-18}=\dfrac{-8x}{-8}\)

<=> \(\sqrt{9x-18}=x\)

<=> 9x - 18 = x²

<=> x² - 9x + 18 = 0

<=> x² - 3x - 6x + 18 = 0

<=> x(x - 3) - 6(x - 3) = 0

<=> (x - 6)(x - 3) = 0

<=> \(\left[{}\begin{matrix}x-6=0\\x-3=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=6\left(tm\right)\\x=3\left(tm\right)\end{matrix}\right.\)

Vậy nghiệm của PT là S = \(\left\{3;6\right\}\)

Thiếu 36 nha.

24 là hiệu của tuổi mẹ trừ tuổi con chứ có phải tuổi mẹ đâu

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