Tìm X biết 0,25 x X = 0.6 - \(3\frac{1}{4}\)
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![](https://rs.olm.vn/images/avt/0.png?1311)
Tìm x biết:
a) (15 × 19 – x – 0,15):0,25 = 15 : 0,25
b)\(2\frac{2}{3}-x=\frac{1}{3}\cdot\frac{6}{2}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(x\cdot\frac{1}{2}+x\cdot\frac{1}{4}+x\cdot\frac{1}{8}=\frac{21}{24}\)
\(x\cdot\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\right)=\frac{7}{8}\)
\(x\cdot\frac{7}{8}=\frac{7}{8}\)
\(\Rightarrow x=\frac{7}{8}\div\frac{7}{8}=1\)
b) \(\left(x+4\right)+\left(x+9\right)+\left(x+14\right)+.....+\left(x+44\right)+\left(x+49\right)=1430\)
\(\left(x+x+x+....+x+x\right)+\left(4+9+14+...+44+49\right)=1430\)
\(10x+265=1430\)
\(10x=1430-265\)
\(10x=1165\)
\(\Rightarrow x=\frac{1165}{10}=116,5\)
c) \(x\cdot0,25-0,5=1\)
\(x\cdot0,25=1+0,5\)
\(x\cdot0,25=1,5\)
\(\Rightarrow x=1,5\div0,25=6\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(\frac{7}{3}\times x-0.6\right)\div3\frac{2}{5}=1\)
\(\left(\frac{7}{3}\times x-\frac{3}{5}\right)\div\frac{17}{5}=1\)
\(\frac{7}{3}\times x-\frac{3}{5}=1\times\frac{17}{5}\)
\(\frac{7}{3}\times x=\frac{17}{5}+\frac{3}{5}\)
\(\frac{7}{3}\times x=4\)
\(x=4\div\frac{7}{3}\)
\(x=4\times\frac{3}{7}\)
\(x=\frac{12}{7}\)
\(x=1\frac{5}{7}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
5.[3/4-2/3x]-13/4=-2{(5/4)2-5/2.1/4+(1/16)2
5.[3/4-2/3x]-13/4=2{25/16-5/8+1/256}
........................=2{400/256-160/250+1/256}
........................=2.241/256
........................=241/128
5.[3/4-2/3x]=241/128+13/4
5.[3/4-2/3x]=241/128+416/128
[3/4-2/3x]=657/128:5
[3/4-2/3x]=657/640
vậy 3/4-2/3x=657/640 và 3/4-2/3x=-657/640
th1:3/4-2/3x va th2:3/4-2/3x=-657/640
còn lại bạn chỉ cần tính kết quả mà dấu[..] là giá tri tuyệt đối đó
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\begin{array}{l}a)x + 0,25 = \frac{1}{2}\\x = \frac{1}{2} - 0,25\\x = \frac{1}{2} - \frac{1}{4}\\x = \frac{2}{4} - \frac{1}{4}\\x = \frac{1}{4}\end{array}\)
Vậy \(x = \frac{1}{4}\)
\(\begin{array}{l}b)x - \left( { - \frac{5}{7}} \right) = \frac{9}{{14}}\\x = \frac{9}{{14}} + \left( { - \frac{5}{7}} \right)\\x = \frac{9}{{14}} + \left( { - \frac{{10}}{{14}}} \right)\\x = \frac{{ - 1}}{{14}}\end{array}\)
Vậy \(x = \frac{{ - 1}}{{14}}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left(0,25-30\%.x\right).\frac{1}{3}-\frac{1}{4}=-5\frac{1}{6}\)
\(< =>\left(\frac{1}{4}-\frac{3x}{10}\right).\frac{1}{3}-\frac{1}{4}=-\frac{30}{6}\)
\(< =>\left(\frac{1}{4}-\frac{3x}{10}\right).\frac{1}{3}=-5+\frac{1}{4}=-\frac{19}{4}\)
\(< =>\frac{1}{4}-\frac{3x}{10}=\frac{-19}{4}.\frac{3}{1}=-\frac{57}{4}\)
\(< =>\frac{-3x}{10}=\frac{-57}{4}-\frac{1}{4}=-\frac{58}{4}\)
\(< =>-12x=-580\)
\(< =>12x=580< =>x=\frac{580}{12}=\frac{145}{3}\)
\(\left(0,25-30\%x\right).\frac{1}{3}-\frac{1}{4}=-5\frac{1}{6}\)
\(\left(\frac{1}{4}-\frac{3}{10}x\right)\frac{1}{3}-\frac{1}{4}=\frac{-31}{6}\)
\(\frac{1}{4}-\frac{3}{10}x=\left(\frac{-31}{6}+\frac{1}{4}\right)\div\frac{1}{3}\)
\(\frac{1}{4}-\frac{3}{10}x=\frac{-59}{4}\)
\(\frac{3}{10}x=\frac{1}{4}-\frac{-59}{4}\)
\(\frac{3}{10}x=15\Leftrightarrow x=50\)
![](https://rs.olm.vn/images/avt/0.png?1311)
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, \(\left|x+\frac{3}{4}\right|-\frac{1}{2}=0\)
\(\Rightarrow\left|x+\frac{3}{4}\right|=\frac{1}{2}\)
\(\Rightarrow\orbr{\begin{cases}x+\frac{3}{4}=\frac{1}{2}\\x+\frac{3}{4}=\frac{-1}{2}\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}x=\frac{-1}{4}\\x=\frac{-5}{4}\end{cases}}\)
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
0,25 x X = 6- \(3\frac{1}{4}\)
0,25 x X = 6 - 13/4
0,25 x X = 11/4
0,25 x X = 2,75
X = 2,75: 0,25
X= 11