`#040911`

`a)`

`3 1/3 x + 16 3/4 = -13,25`

`=> 3 1/3 x = -13,25 - 16 3/4`

`=> 3 1/3 x = -30`

`=> x = -30 \div 3 1/3`

`=> x =-9`

Vậy, `x = -9`

`b)`

`3 2/7*x - 1/8 = 2 3/4`

`=> 3 2/7x = 2 3/4 + 1/8`

`=> 3 2/7x = 23/8`

`=> x = 23/8 \div 3 2/7`

`=> x = 7/8`

Vậy, `x = 7/8`

`c)`

`x \div 4 1/3 = -2,5`

`=> x = -2,5 * 4 1/3`

`=> x = -65/6`

Vậy, `x = -65/6`

`d)`

`( (3x)/7 + 1) \div (-4) = (-1)/28`

`=> (3x)/7 +1 = (-1)/28 * (-4)`

`=> (3x)/7 + 1 = 1/7`

`=> (3x)/7 = 1/7 - 1`

`=> (3x)/7 = -6/7`

`=> 3x = -6`

`=> x = -6 \div 3`

`=> x = -2`

Vậy, `x = -2.`

a

=>10/3 . x + 16 + 3/4 = -13,25

=>10/3 x + 3/4 = -29,25

=>10/3 x = -30

=>x=-30 : 10/3

=>x=-30 . 3/10

=>x=-9

b.

=>23/7 x - 1/8 = = 11/4

=>23/7 x = 11/4 + 1/8

=>23/7 x= 22/8 + 1/8

=>23/7 x= 23/8

=>x=23/8 : 23/7

=>x=23/8 . 7/23

=>x=7/8

c.

=>x : 13/3 =-5/2

=>x=-5/2 . 13/3

=>x=-65/6

d.

=>3x/7 +1 = (-1/28) . (-4)

=>3x/7 + 1 = 1/7

=>3x/7 = -6/7

=>3x=-6

=>x=-2

a) \(3\dfrac{1}{3}x+16\dfrac{3}{4}=-13,25\)

\(\Rightarrow\dfrac{10}{3}x+\dfrac{67}{4}=-\dfrac{53}{4}\)

\(\Rightarrow\dfrac{10}{3}x=-30\)

\(\Rightarrow x=-30:\dfrac{10}{3}\)

\(\Rightarrow x=-9\)

b) \(3\dfrac{2}{7}x-\dfrac{1}{8}=2\dfrac{3}{4}\)

\(\Rightarrow\dfrac{23}{7}x-\dfrac{1}{8}=\dfrac{11}{4}\)

\(\Rightarrow\dfrac{23}{7}x=\dfrac{11}{4}+\dfrac{1}{8}\)

\(\Rightarrow\dfrac{23}{7}x=\dfrac{23}{8}\)

\(\Rightarrow x=\dfrac{23}{8}:\dfrac{23}{7}\)

\(\Rightarrow x=\dfrac{7}{8}\)

c) \(x:4\dfrac{1}{3}=-2,5\)

\(\Rightarrow x:\dfrac{13}{3}=-\dfrac{5}{2}\)

\(\Rightarrow x=-\dfrac{5}{2}\cdot\dfrac{13}{3}\)

\(\Rightarrow x=-\dfrac{65}{6}\)

d) \(\left(\dfrac{3x}{7}+1\right):\left(-4\right)=\dfrac{-1}{28}\)

\(\Rightarrow\dfrac{3x}{7}+1=\dfrac{-1}{28}\cdot-4\)

\(\Rightarrow\dfrac{3x}{7}+1=\dfrac{1}{7}\)

\(\Rightarrow\dfrac{3x}{7}=-\dfrac{6}{7}\)

\(\Rightarrow x=-\dfrac{6}{7}:\dfrac{3}{7}\)

\(\Rightarrow x=-2\)

\(a,\dfrac{3}{7}-x=\dfrac{1}{2}x-3\)

\(\Rightarrow-x-\dfrac{1}{2}x=-3-\dfrac{3}{7}\)

\(\Rightarrow-\dfrac{3}{2}x=-\dfrac{24}{7}\)

\(\Rightarrow x=-\dfrac{24}{7}:\left(-\dfrac{3}{2}\right)\)

\(\Rightarrow x=\dfrac{16}{7}\)

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

\(\Rightarrow5x+2x=\dfrac{5}{3}+\dfrac{2}{3}\)

\(\Rightarrow7x=\dfrac{7}{3}\)

\(\Rightarrow x=\dfrac{7}{3}:7\)

\(\Rightarrow x=\dfrac{1}{3}\)

#Toru

a: 3/7-x=1/2x-3

=>-3/2x=-3+3/7

=>-1/2x=-1+1/7=-6/7

=>1/2x=6/7

=>x=6/7*2=12/7

b: =>5x+2x=5/3+2/3

=>7x=7/3

=>x=1/3

a: \(-4x\left(x-5\right)-2x\left(8-2x\right)=-3\)

=>\(-4x^2+20x-16x+4x^2=-3\)

=>4x=-3

=>\(x=-\dfrac{3}{4}\)

b: \(-7\left(x+9\right)-3\left(5-x\right)=2\)

=>\(-7x-63-15+3x=2\)

=>\(-4x-78=2\)

=>\(-4x=78+2=80\)

=>\(x=\dfrac{80}{-4}=-20\)

a: Ta có: \(\left(2x+1\right)^2-4\left(x+2\right)^2=9\)

\(\Leftrightarrow4x^2+4x+1-4x^2-16x-16=9\)

\(\Leftrightarrow-12x=24\)

hay x=-2

b: Ta có: \(\left(x+3\right)^2-\left(x-4\right)\left(x+8\right)=1\)

\(\Leftrightarrow x^2+6x+9-x^2-4x+32=1\)

\(\Leftrightarrow2x=-40\)

hay x=-20

Bài 1: 

a) Ta có: \(\dfrac{17}{6}-x\left(x-\dfrac{7}{6}\right)=\dfrac{7}{4}\)

\(\Leftrightarrow\dfrac{17}{6}-x^2+\dfrac{7}{6}x-\dfrac{7}{4}=0\)

\(\Leftrightarrow-x^2+\dfrac{7}{6}x+\dfrac{13}{12}=0\)

\(\Leftrightarrow-12x^2+14x+13=0\)

\(\Delta=14^2-4\cdot\left(-12\right)\cdot13=196+624=820\)

Vì Δ>0 nên phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{14-2\sqrt{205}}{-24}=\dfrac{-7+\sqrt{205}}{12}\\x_2=\dfrac{14+2\sqrt{2015}}{-24}=\dfrac{-7-\sqrt{205}}{12}\end{matrix}\right.\)

b) Ta có: \(\dfrac{3}{35}-\left(\dfrac{3}{5}-x\right)=\dfrac{2}{7}\)

\(\Leftrightarrow\dfrac{3}{5}-x=\dfrac{3}{35}-\dfrac{10}{35}=\dfrac{-7}{35}=\dfrac{-1}{5}\)

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

ai giúp mik vs

Bài 3: 

a) Ta có: \(2x-3=x+\dfrac{1}{2}\)

\(\Leftrightarrow2x-x=\dfrac{1}{2}+3\)

\(\Leftrightarrow x=\dfrac{7}{2}\)

b) Ta có: \(4x-\left(x+\dfrac{1}{2}\right)=2x-\left(\dfrac{1}{2}-5\right)\)

\(\Leftrightarrow3x-\dfrac{1}{2}-2x+\dfrac{1}{2}-5=0\)

\(\Leftrightarrow x=5\)

Lời giải:

a. $2x^2+3(x-1)(x+1)=5x(x+1)$

$\Leftrightarrow 2x^2+3x^2-3=5x^2+5x$

$\Leftrightarrow 5x^2-3=5x^2+5x$
$\Leftrightarrow 5x=-3$

$\Leftrightarrow x=\frac{-3}{5}$

b.

PT $\Leftrightarrow (-5x^2-2x+16)+4(x^2-x-2)=4-x^2$

$\Leftrightarrow -x^2-6x+8=4-x^2$

$\Leftrightarrow -6x+8=4$
$\Leftrightarrow -6x=-4$

$\Leftrightarrow x=\frac{2}{3}$

c.

PT $\Leftrightarrow 4(x^2+4x-5)-(x^2+7x+10)=3(x^2+x-2)$

$\Leftrightarrow 4x^2+16x-20-x^2-7x-10=3x^2+3x-6$

$\Leftrightarrow 3x^2+9x-30=3x^2+3x-6$

$\Leftrightarrow 6x=24$

$\Leftrightarrow x=4$

Bài 2: 

a: \(\left(6x-39\right):7=3\)

\(\Leftrightarrow6x-39=21\)

hay x=10

a)\(=\dfrac{3}{3}+\dfrac{4}{3}=\dfrac{7}{3}\)

b)\(=\dfrac{5}{9}\times\dfrac{3}{2}=\dfrac{15}{18}=\dfrac{5}{6}\)

d)\(=\left(\dfrac{12}{8}-\dfrac{3}{8}\right)\times2=\dfrac{9}{8}\times2=\dfrac{18}{8}=\dfrac{9}{4}\)

c)\(=\dfrac{4}{3}-\dfrac{5}{6}=\dfrac{8}{6}-\dfrac{5}{6}=\dfrac{3}{6}=\dfrac{1}{2}\)

a) 1 + 4/3 = 7/3

b) 5/9 : 2/3 = 5/6

c ) 4/3 -1/3 x 5/2

= 1 x 5/2

= 5/2

d) ( 3/2 - 3/8) : 1/2

= 9/8 : 1/2

= 9/4

e) 15/16 : 3/8 x 3/4 

= 5/2 x 3/4

= 15/8

f) 7/19 x 1/3 x 7/19 x 2/3

= 7/19 x (1/3 x 2/3)

= 7/19 x 2/9

= 14/171

g) 3/5 x 8/27 x 25/3

= 3/5 x 25/3 x 8/27 

= 5 x 8/27

= 40/27

h) 1/5 + 4/11 + 4/5 + 7/11

= (1/5 + 4/5) + (4/11 + 7/11)

= 1 + 1

= 2

e)\(\dfrac{15}{16}\times\dfrac{8}{3}\times\dfrac{3}{4}=\dfrac{360}{192}=\dfrac{15}{8}\)

f) \(=\dfrac{7}{19}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)=\dfrac{7}{19}\times\dfrac{3}{3}=\dfrac{7}{19}\)

g)\(=\dfrac{600}{120}=\dfrac{600:120}{120:120}=\dfrac{5}{1}=5\)

h)\(=\left(\dfrac{1}{5}+\dfrac{4}{5}\right)+\left(\dfrac{4}{11}+\dfrac{7}{11}\right)=\dfrac{5}{5}+\dfrac{11}{11}=1+1=2\)

Giải:

a)-3/10-(-1/5)+x)=-3/2

             -1/5+x   =-3/10-(-3/2)

              -1/5+x   =6/5

                       x   =6/5-(-1/5)

                       x   =7/5

b)-(-x+3/4)-12/8.(-32/15)=-(-1/2)

           x-3/4+16/5          =1/2

           x-3/4                =1/2-16/5

           x                           =-27/10

           x                           =-27/10+3/4

           x                           =-39/20

c)x-3/x+5=4/3

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

     3x-9   =4x+20

     3x-4x =20+9

     -1x     =29

        x     =-29

Câu b cậu nên tính lại cho kĩ nhé, ấn máy tính dễ nhầm lắm đấy!

Mk phải ấn: -(39/20+3/4)-12/8.-32/15=1/2

Vì x là số âm mà đằng trước x là dấu ''-'' nên -(-39/20)=39/20 ; -(-1/2)=1/2

Chúc bạn học tốt!