`c)1/4x+2/5=7/5`

`=>1/4x=7/5-1/5=1`

`=>x=1:1/4=4`

Vậy `x=4` 

`a)2x-2/3=-3/4`

`=>2x=-3/4+2/3=-1/12`

`=>x=-1/24`

Vậy `x=-1/24`

`b)x:3/4+1/4=-2/3`

`=>x:3/4=-2/3-1/4=-11/4`

`=>x=-11/4 xx 3/4=-33/16`

Vậy `x=-33/16`

Mình không viết lại đề nhé

a) -12x + 60 + 21 - 7x = 5

-19x = 5 - 71

-19x = -76

x = 4

b) 3 - 17 + x = 289 - 36 - 289

x = -22

\(a,-12.\left(x-5\right)+7.\left(3-x\right)=5\)

\(=.-12x+60+21-7x=5\)

\(=>-19x=5-60-21=-76\)

\(=>x=\frac{-76}{-19}=\frac{76}{19}=4\)

\(b,3-\left(17-x\right)=289-\left(36+289\right)\)

\(=>3-17+x=-36\)

\(=>x=-36+17-3=-22\)

a) -12(x-5)+7(3-x)=5

<=> -12x+60+21-7x=5

<=> 9+53x=5

<=> 53x=-4

<=> x=\(\frac{-4}{53}\)

b) 3-(17-x)=289-(36+289)

<=> 3-17+x=289-36-289

<=> -14+x=-36

<=> x=-22

\(a,50\%x-0,2+x=\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{1}{2}x-0,2+x=\dfrac{4}{5}\)

\(\Leftrightarrow\dfrac{1}{2}x+x=\dfrac{4}{5}+0,2\)

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

\(\Leftrightarrow\dfrac{3}{2}x=1\)

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

\(b,\left(x-\dfrac{3}{4}\right):\dfrac{1}{2}+\dfrac{3}{2}=\dfrac{25}{2}\)

\(\Leftrightarrow\left(x-\dfrac{3}{4}\right).2=\dfrac{25}{2}-\dfrac{3}{2}\)

\(\Leftrightarrow\left(x-\dfrac{3}{4}\right).2=\dfrac{22}{2}\)

\(\Leftrightarrow x-\dfrac{3}{4}=11:2\)

\(\Leftrightarrow x=\dfrac{11}{2}+\dfrac{3}{4}\)

\(\Leftrightarrow x=\dfrac{25}{4}\)

a, ( 44 - x ) / 3 = ( x - 12 ) / 5

=> 5 ( 44 - x  ) = 3 ( x - 12 )

     220 - 5x     = 3x  - 36

     - 5x - 3x     = - 36 - 220

      - 8 x          = - 256

           x          = 32

b , ( 3 - x ) / 4 = ( 2x + 7 ) / 5

=> 5 ( 3 - x )   = 4 ( 2x + 7 )

     15 - 5x      = 8 x  + 28

     - 5 x - 8 x  = 28 - 15

        - 13 x     = 13

               x     = -1

a, \(\frac{\left(44-x\right)}{3}=\frac{\left(x-12\right)}{5}\)

 => (44 - x) . 5 = (x - 12) . 3

 => 44 - x . 5   = x - 12 .3

 => 44 - x . 5   = x - 36

 => x5 + x        = - 36 - 44

 => x5 + x        = - 80

=> x . (5 + 1)    = - 80

=> x . 6           = - 80

=> x                = - 80 : 6

=> x                = - 13,3

b, \(\frac{\left(3-x\right)}{4}=\frac{\left(2x+7\right)}{5}\)

=> (3 - x) . 5 = (2x + 7) . 4

=> 3 - x . 5   = 2x + 7 . 4

=> 3 - x . 5   = 2x + 28

=> -x . 5 + 2x = 28 - 3

=> -x . 5 + 2x = 25

=>  x . 5 + 2x = 25

=>  x . (5 + 2) = 25

=>  x . 7         = 25

=>  x              = 25 : 7

=>  x              = 3,57

a)(44-x).5=(x-12).3

44.5-x.5=x.3-12.3

220-x.5=x.3-36

220-x.5-x.3=-36

x.5-x.3=220+36

x.(5-3)=256

x.2=256

x=256:2

x=128

b: \(\dfrac{5}{7}-\dfrac{2}{3}\cdot x=\dfrac{4}{5}\)

=>\(\dfrac{2}{3}x=\dfrac{5}{7}-\dfrac{4}{5}=\dfrac{25-28}{35}=\dfrac{-3}{35}\)

=>\(x=-\dfrac{3}{35}:\dfrac{2}{3}=\dfrac{-3}{35}\cdot\dfrac{3}{2}=-\dfrac{9}{70}\)
c: \(\dfrac{1}{2}x+\dfrac{3}{5}x=-\dfrac{2}{3}\)

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

=>\(x\cdot\dfrac{5+6}{10}=\dfrac{-2}{3}\)

=>\(x\cdot\dfrac{11}{10}=-\dfrac{2}{3}\)

=>\(x=-\dfrac{2}{3}:\dfrac{11}{10}=-\dfrac{2}{3}\cdot\dfrac{10}{11}=\dfrac{-20}{33}\)

d: \(\dfrac{4}{7}\cdot x-x=-\dfrac{9}{14}\)

=>\(\dfrac{-3}{7}\cdot x=\dfrac{-9}{14}\)

=>\(\dfrac{3}{7}\cdot x=\dfrac{9}{14}\)

=>\(x=\dfrac{9}{14}:\dfrac{3}{7}=\dfrac{9}{14}\cdot\dfrac{7}{3}=\dfrac{3}{2}\)

a)(x+3)2-x2+15=2x+6-2x+15=1

                        =21=1

Bạn chép sai đầu bài à

x2 là x^2 à

\(a,\Rightarrow x^2+4x+25-x^2=3\\ \Rightarrow4x=-22\Rightarrow x=-\dfrac{11}{2}\\ b,\Rightarrow\left(2x-3-4x-3\right)\left(2x-3+4x+3\right)=0\\ \Rightarrow6x\left(-2x-6\right)=0\Rightarrow\left[{}\begin{matrix}x=-3\\x=0\end{matrix}\right.\)

a. -6.x=18

<=> x=-3

Vậy x=-3

b.2.x-(-3)=7

<=> 2x=4

<=>x=2

Vậy x=2

c.(x-5).(x+6)=0

<=> x-5=0 hoặc x+6=0

<=> x=5 hoặc x=-6

Vậy \(x\in\left\{5;-6\right\}\)

Trả lời:

\(a,\)\(-6x=18\)

\(\Leftrightarrow x=-3\)

Vậy\(x=-3\)

\(b,\)\(2x-\left(-3\right)=7\)

\(\Leftrightarrow2x=4\)

\(\Leftrightarrow x=2\)

Vậy\(x=2\)

\(c,\)\(\left(x-5\right)\left(x+6\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}x-5=0\\x+6=0\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}x=5\\x=-6\end{cases}}\)

Vậy\(x\in\left\{5;-6\right\}\)

Hok tốt!

Good girl

a) -6x=18

<=> x=-3

b) 2x-(-3)=7

<=> 2x+3=7

<=> 2x=4

<=> x=2

c) (x-5)(x+6)=0

<=> x-5=0 hoặc x+6=0

<=> x=5 hoặc x=-6