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0,25 x X =12,56-\(3\frac{1}{4}\)

0,25 xX  =12,56-\(\frac{13}{4}\)

0,25 x X =12,56-3,25

0,25 x X =9,31

       X =9,31:0,25

     X=37,24

Vậy X=37,24

Chúc bn học tốt

29 tháng 12 2022

\(a.x\times6+x:0,25=27,9\)

\(x\times6+x\times4=27,9\)

\(x\times\left(6+4\right)=27,9\)

\(x\times10=27,9\)

\(x=27,9:10\)

\(x=2,79\)

 

b. \(32,9:x+3,16=12,56\)

\(32,9:x=12,56-3,16\)

\(32,9:x=9,4\)

\(x=32,9:9,4\)

\(x=3,5\)

26 tháng 3 2018

12,56 x X + X : 0,25 = 69,552

12,56 x X + X x 4 = 69,552

X x ( 12,56 + 4 ) = 69,552

X x 16,56 = 69,552

X = 69,552 : 16,56

X = 4,2

26 tháng 3 2018

12 , 56 x X + X : 0 , 25 = 69 , 552 

12 , 56 x X + X x 4       = 69 , 552 

X x ( 12 , 56 + 4 )         = 69 , 552 

X x 16 , 56                   = 69 , 552 

       X                          = 69 , 552  :16 , 56

      X                           =  4 , 2 

 Vậy X = 4 , 2 

Tham khảo nha !!! 

10 tháng 12 2019

a) \(3,6-\left|x-0,4\right|=0\)

\(\Leftrightarrow\left|x-0,4\right|=3,6\)

\(\Leftrightarrow\left[{}\begin{matrix}x-0,4=3,6\\x-0,4=-3,6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=-3,2\end{matrix}\right.\)

Vậy \(x\in\left\{4;-3,2\right\}\)

b) Ta có:

\(\frac{x}{2}=y=\frac{z}{3}=\frac{2y}{2}=\frac{x-2y+z}{2-2+3}=\frac{210}{3}=70\)

\(\Rightarrow\left\{{}\begin{matrix}\frac{x}{2}=70\\y=70\\\frac{z}{3}=70\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x=140\\y=70\\z=210\end{matrix}\right.\)

Vậy \(x=140\); \(y=70\); \(z=210\)

c)\(\left|x+0,25\right|-4=\frac{1}{4}\)

\(\Leftrightarrow\left|x+\frac{1}{4}\right|=\frac{17}{4}\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\frac{1}{4}=\frac{17}{4}\\x+\frac{1}{4}=\frac{-17}{4}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=\frac{-9}{2}\end{matrix}\right.\)

Vậy \(x\in\left\{4;\frac{-9}{2}\right\}\)

d) \(x:\left(0,25\right)^4=\left(0,5\right)^2\)

\(\Leftrightarrow x=\left(0,25\right)^4.\left(0,5\right)^2\)

\(\Leftrightarrow x=\left(0,5\right)^8.\left(0,5\right)^2\)

\(\Leftrightarrow x=\left(0,5\right)^{10}=\left(\frac{1}{2}\right)^{10}=\frac{1}{2^{10}}=\frac{1}{1024}\)

Vậy \(x=\frac{1}{1024}\)

e) \(3^{x-1}+5.3^{x-1}=162\)

\(\Leftrightarrow6.3^{x-1}=162\)

\(\Leftrightarrow3^{x-1}=27\)

\(\Leftrightarrow3^{x-1}=3^3\)

\(\Leftrightarrow x-1=3\)

\(\Leftrightarrow x=4\)

f) \(\frac{x}{-25}=\frac{2}{5}\)

\(\Leftrightarrow x=\left(-25\right).\frac{2}{5}=-10\)

Vậy \(x=-10\)

g) \(\left|x+\frac{3}{4}\right|-\frac{3}{4}=\sqrt{\frac{1}{9}}\)

\(\Leftrightarrow\left|x+\frac{3}{4}\right|-\frac{3}{4}=\frac{1}{3}\)

\(\Leftrightarrow\left|x+\frac{3}{4}\right|=\frac{13}{12}\)

\(\Leftrightarrow\left[{}\begin{matrix}x+\frac{3}{4}=\frac{13}{12}\\x+\frac{3}{4}=-\frac{13}{12}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{1}{3}\\x=-\frac{11}{6}\end{matrix}\right.\)

Vậy \(x\in\left\{\frac{1}{3};-\frac{11}{6}\right\}\)

10 tháng 12 2019

a) \(3,6-\left|x-0,4\right|=0\)

\(\Rightarrow\left|x-0,4\right|=3,6-0\)

\(\Rightarrow\left|x-0,4\right|=3,6.\)

\(\Rightarrow\left[{}\begin{matrix}x-0,4=3,6\\x-0,4=-3,6\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=3,6+0,4\\x=\left(-3,6\right)+0,4\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-3,2\end{matrix}\right.\)

Vậy \(x\in\left\{4;-3,2\right\}.\)

c) \(\left|x+0,25\right|-4=\frac{1}{4}\)

\(\Rightarrow\left|x+\frac{1}{4}\right|=\frac{1}{4}+4\)

\(\Rightarrow\left|x+\frac{1}{4}\right|=\frac{17}{4}.\)

\(\Rightarrow\left[{}\begin{matrix}x+\frac{1}{4}=\frac{17}{4}\\x+\frac{1}{4}=-\frac{17}{4}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\frac{17}{4}-\frac{1}{4}\\x=\left(-\frac{17}{4}\right)-\frac{1}{4}\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=4\\x=-\frac{9}{2}\end{matrix}\right.\)

Vậy \(x\in\left\{4;-\frac{9}{2}\right\}.\)

d) \(x:\left(0,25\right)^4=\left(0,5\right)^2\)

\(\Rightarrow x:\left(0,25\right)^4=0,25\)

\(\Rightarrow x=\left(0,25\right).\left(0,25\right)^4\)

\(\Rightarrow x=\left(0,25\right)^5\)

\(\Rightarrow x=\frac{1}{1024}\)

Vậy \(x=\frac{1}{1024}.\)

Chúc bạn học tốt!

2 tháng 12 2019

Violympic toán 8Violympic toán 8

11 tháng 7 2017

a) x=5397/20

b)x=5/3

13 tháng 6 2018

a) (15 x 19 - x - 0,15) : 0,25 = 15 : 0,15

    (285 - x - 0,15) : 0,25 = 60

    (285 - x - 0,25) = 60 : 0,25

    ( 285 - x - 0,25) = 15

      285 - x = 15 + 0,25

      285 - x = 15,25

              x = 285 - 15,25 

              x = 269,75

3 tháng 9 2018

a, \(7\left(x-1\right)+2x\left(1-x\right)=0\)

\(\Rightarrow\left(7-2x\right)\left(x-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}7-2x=0\\x-1=0\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{7}{2}\\x=1\end{cases}}\)

b, \(0,25-\left|3,5-x\right|=0\)

\(\Rightarrow\left|3,5-x\right|=2,5\)

\(\Rightarrow\orbr{\begin{cases}3,5-x=2,5\\3,5-x=-2,5\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=1\\x=6\end{cases}}\)

c, \(\left|x+\frac{3}{4}\right|-\frac{1}{2}=0\)

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

\(\Rightarrow\orbr{\begin{cases}x+\frac{3}{4}=\frac{1}{2}\\x+\frac{3}{4}=\frac{-1}{2}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{-1}{4}\\x=\frac{-5}{4}\end{cases}}\)

3 tháng 9 2018

a) 7.(x-1) + 2x.(1-x) = 0

7.(x-1) - 2x.(x-1) = 0

(x-1).(7-2x) = 0

=> (x-1) = 0 => x = 1

7-2x = 0 => 2x = 7 => x = 7/2

KL:...

b) 0,25 - | 3,5-x| = 0

=> |3,5 - x| = 0,25

TH1: 3,5 - x = 0,25

x = 3,25

TH2: 3,5 - x = -0,25

x = 3,75

phần c bn dựa vào phần b mak lm nha

HQ
Hà Quang Minh
Giáo viên
19 tháng 9 2023

\(\begin{array}{l}a)3{x^7}:\dfrac{1}{2}{x^4} = (3:\dfrac{1}{2}).({x^7}:{x^4}) = 6{x^3}\\b)( - 2x):x = [( - 2):1].(x:x) =  - 2\\c)0,25{x^5}:( - 5{x^2}) = [0,25:( - 5)].({x^5}:{x^2}) =  - 0,05.{x^3}\end{array}\)

20 tháng 1 2020

cái này trong sách í

20 tháng 1 2020

a) \(\frac{3x-2}{2}=\frac{1-2x}{3}\)

\(\Leftrightarrow3\left(3x-2\right)=2\left(1-2x\right)\)

\(\Leftrightarrow9x-6=2-4x\)

\(\Leftrightarrow13x-8=0\)

\(\Leftrightarrow x=\frac{8}{13}\)

b) \(\frac{x-1}{3}+2=3-\frac{2x+5}{4}\)

\(\Leftrightarrow\frac{4\left(x-1\right)+24}{12}=\frac{36-3\left(2x+5\right)}{12}\)

\(\Leftrightarrow4x-4+24=36-6x-15\)

\(\Leftrightarrow4x+20=-6x+21\)

\(\Leftrightarrow10x=1\)

\(\Leftrightarrow x=\frac{1}{10}\)

c) \(\frac{x-1}{5}+x=\frac{x+1}{7}\)

\(\Leftrightarrow\frac{7\left(x-1\right)+35x}{35}=\frac{5\left(x+1\right)}{7}\)

\(\Leftrightarrow7x-7+35x=5x+5\)

\(\Leftrightarrow37x=12\)

\(\Leftrightarrow x=\frac{12}{37}\)

d) \(2.\left(x-2.5\right)=0,25+\frac{4x-3}{8}\)

\(\Leftrightarrow8\left(x-2,5\right)=2+4x-3\)

\(\Leftrightarrow8x-20=4x-1\)

\(\Leftrightarrow4x=19\)

\(\Leftrightarrow x=\frac{4}{19}\)

a) Ta có: \(\left(x-2\right)^3+\frac{8}{27}=0\)

\(\Leftrightarrow\left(x-2\right)^3=\frac{-8}{27}\)

\(\Leftrightarrow\left(x-2\right)^3=\left(-\frac{2}{3}\right)^3\)

\(\Leftrightarrow x-2=\frac{-2}{3}\)

hay \(x=\frac{-2}{3}+2=\frac{4}{3}\)

Vậy: \(x=\frac{4}{3}\)

b) Ta có: \(4\frac{1}{3}:\frac{x}{4}=6:0,3\)

\(\Leftrightarrow\frac{13}{3}\cdot\frac{4}{x}=20\)

\(\Leftrightarrow\frac{4}{x}=20:\frac{13}{3}=20\cdot\frac{3}{13}=\frac{60}{13}\)

hay \(x=\frac{13\cdot4}{60}=\frac{13}{15}\)

Vậy: \(x=\frac{13}{15}\)

c) Ta có: \(\left(0,25-30\%x\right)\cdot\frac{1}{3}-\frac{1}{4}=5\frac{1}{6}\)

\(\Leftrightarrow\left(\frac{1}{4}-\frac{3x}{10}\right)\cdot\frac{1}{3}=\frac{31}{6}+\frac{1}{4}=\frac{65}{12}\)

\(\Leftrightarrow\frac{1}{4}-\frac{3x}{10}=\frac{65}{12}:\frac{1}{3}=\frac{65}{12}\cdot3=\frac{65}{4}\)

\(\Leftrightarrow\frac{3x}{10}=\frac{1}{4}-\frac{65}{4}=-16\)

\(\Leftrightarrow3x=-160\)

hay \(x=\frac{-160}{3}\)

Vậy: \(x=\frac{-160}{3}\)

d) Ta có: \(\frac{x-2}{-\frac{2}{9}}=\frac{-2}{x-2}\)

\(\Leftrightarrow\left(x-2\right)^2=-2\cdot\left(-\frac{2}{9}\right)=\frac{4}{9}\)

\(\Leftrightarrow\left[{}\begin{matrix}x-2=\frac{2}{3}\\x-2=-\frac{2}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{2}{3}+2\\x=\frac{-2}{3}+2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\frac{8}{3}\\x=\frac{4}{3}\end{matrix}\right.\)

Vậy: \(x\in\left\{\frac{8}{3};\frac{4}{3}\right\}\)

30 tháng 3 2020

a/ (x - 2)3 + \(\frac{8}{27}\) = 0

=> (x - 2)3 = 0 - \(\frac{8}{27}\) = \(\frac{-8}{27}\)

=> x - 2 = \(-\frac{2}{3}\)

=> x = \(-\frac{2}{3}+2=\frac{4}{3}\)

b/ \(4\frac{1}{3}:\frac{x}{4}=6:0,3\)

=> \(4\frac{1}{3}:\frac{x}{4}=6:\frac{3}{10}=6.\frac{10}{3}=20\)

=> \(\frac{x}{4}=4\frac{1}{3}:20=\frac{13}{3}.\frac{1}{20}=\frac{13}{60}\)

=> \(x=\frac{13}{60}.4=\frac{13}{15}\)

c/ \(\left(0,25-30\%x\right).\frac{1}{3}-\frac{1}{4}=5\frac{1}{6}\)

=> \(\left(0,25-30\%x\right).\frac{1}{3}=5\frac{1}{6}+\frac{1}{4}=\frac{65}{12}\)

=> \(0,25-\frac{30}{100}x=\frac{65}{12}:\frac{1}{3}=\frac{65}{12}.3=\frac{65}{4}\)

=> \(\frac{3}{10}x=0,25-\frac{65}{4}=\frac{1}{4}-\frac{65}{4}=-\frac{64}{4}=-16\)

=> \(x=-16:\frac{3}{10}=-16.\frac{10}{3}=-\frac{160}{3}\)