a) Ta có: \(4\left(x-2\right)-2\left(x+3\right)=-28\)

\(\Leftrightarrow4x-8-2x-6+28=0\)

\(\Leftrightarrow2x+14=0\)

\(\Leftrightarrow2x=-14\)

hay x=-7

Vậy: x=-7

b) Ta có: \(3x+7-9x=-11\)

\(\Leftrightarrow-6x+7+11=0\)

\(\Leftrightarrow-6x+18=0\)

\(\Leftrightarrow-6x=-18\)

hay x=3

Vậy: x=3

bị sang chấn tâm lí cái câu hỏi cụa bn ghê , tách `5->6` câu th bn:)

:v què tay hmu :<

từ bài 2 trở đi là lú rồi=)))

Đặt \(\sqrt{\dfrac{4x+9}{28}}=y+\dfrac{1}{2}\left(y\ge-\dfrac{1}{2}\right)\).

Ta có hpt:

\(\left\{{}\begin{matrix}14y^2+14y=2x+1\\14x^2+14x=2y+1\end{matrix}\right.\)

\(\Rightarrow14\left(x^2-y^2\right)+16\left(x-y\right)=0\Leftrightarrow\left[{}\begin{matrix}x-y=0\\x+y=\dfrac{-8}{7}\end{matrix}\right.\).

Đến đây thế vào là được.

Pt\(\Leftrightarrow\left(x^4-4x^2\right)-\left(5x^2-20\right)=0\Leftrightarrow\left(x^2-4\right)\left(x^2-5\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x^2=4\\x^2=5\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2;x=-2\\x=\sqrt{5};x=-\sqrt{5}\end{cases}}}\)

Vì x nguyên dương nên \(\Rightarrow\orbr{\begin{cases}x=2\\x=\sqrt{5}\end{cases}}\)

Vậy \(\orbr{\begin{cases}x=2\\x=\sqrt{5}\end{cases}}\)

a: =>x/27+1=-2/3

=>x/27=-5/3

=>x=-45

b: \(\Leftrightarrow x-4=\dfrac{2}{5}:\dfrac{20}{21}=\dfrac{2}{5}\cdot\dfrac{21}{20}=\dfrac{42}{100}=\dfrac{21}{50}\)

=>x=221/50

c: \(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{4}{60}=\dfrac{1}{15}\)

=>x=1/15-2/3=1/15-10/15=-9/15=-3/5

d: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{15}{14}\cdot\dfrac{21}{20}\)

=>\(x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{3}{2}\cdot\dfrac{3}{4}=\dfrac{1}{5}-\dfrac{9}{8}=\dfrac{-37}{40}\)

=>x=-37/24

e: =>-3/7x=84/45

=>x=-196/45

f: =>11/10x=-2/3

=>x=-20/33

-2.(-x-5)+28=20-3.(x+4)

   2x+10+28=20-3x-12

         2x+3x=20-12-10-28

               5x=-30

                 x=-30:5

                 x=-6

Vậy x=-6          

-2.(- x - 5 ) + 28 = 20 - 3.(x + 4 )

2x + 10 + 28 = 20 -3x - 12

2x + 3x = 20 - 12 - 10 - 28

5x = -30

x = -6