Tìm x biết 4.x-54:17=21
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![](https://rs.olm.vn/images/avt/0.png?1311)
a, x + 26 = 39 + (-5)
x + 26 = 39 - 5
x + 26 = 34
x = 34 - 26
x = 8
b, |x| + 50 = (-|-26|) +76
|x| +50 = (-26) +76
|x| +50 = 76 - 26
|x| +50 = 50
|x| = 50 -50
|x| = 0
c, |x| + 17 = (-21)+19
|x| + 17 = - (21-19)
|x| + 17 = - 2
|x| không tồn tại
d. |x-21|= 2.(|-11| + |-3|)
|x-21|= 2.(11+3)
|x-21|= 2.14
|x-21|= 28
x = 28+21 hoặc 21-28
x = 49 hoặc -7
e. hình như lộn đề vì |x-54|-7|
![](https://rs.olm.vn/images/avt/0.png?1311)
a) 150 : [17 - (2x - 3)] = 350
=> 17 - (2x - 3) = \(\frac{150}{350}=\frac{3}{7}\)
=> 2x - 3 = \(17-\frac{3}{7}=\frac{116}{7}\)
=> 2x = \(\frac{116}{7}+3\)
=> 2x = \(\frac{137}{7}\)
=> x = \(\frac{137}{7}:2=\frac{137}{14}\)
b) 4 . [105 - (x - 9)] - 486 = 0
=> 4. [105 - (x - 9)] = 486
=> 105 - (x - 9) = 243/2
=> x - 9 = \(105-\frac{243}{2}=-\frac{33}{2}\)
=> x = \(-\frac{33}{2}+9=-\frac{15}{2}\)
c) 1000 - 2{600 - 4.[198 - 7.(21 - 7)]}.x = 200
=> 1000 - 2{600 - 4.[198 - 7.14]}.x = 200
=> 1000 - 2{600 - 4.[198 - 98].x = 200
=> 1000 - 2{600 - 4.100}.x = 200
=> 1000 - 2{600 -400}.x = 200
=> 1000 - 2.200.x = 200
=> 2.200.x = 800
=> 400.x = 800
=> x = 2
Câu 2 :
a) 350 : [19 - (7x - 3)] = 350
=> 19 - (7x - 3) = 1
=> 7x - 3 = 18
=> 7x = 21
=> x = 3
b) 7.[109 - (x - 9)] - 420 = 0
=> 7.[109 - (x - 9)] = 420
=> 109 - (x - 9) = 60
=> x - 9 = 49
=> x = 49 + 9 = 58
c) 254 - 2{200 - 4.[90 - 7.(19 - 9)]}.x = 54
=> 254 - 2{200 - 4.[90 - 7.10]}.x = 54
=> 254 - 2{200 - 4[90 - 70]} . x= 54
=> 254 - 2{200 - 4.20} . x = 54
=> 254 - 2{200 - 80}.x = 54
=> 254 - 2.120 . x= 54
=> 2.120.x = 200
=> 240.x = 200
=> \(x=\frac{5}{6}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 1:
a) \(\frac{16}{15}.\frac{\left(-5\right)}{14}.\frac{54}{24}.\frac{56}{21}\)
\(=\frac{4.2.2}{5.3}.\frac{\left(-5\right)}{2.7}.\frac{3.3}{4}.\frac{8}{3}\)
\(=\frac{4.2.2.\left(-5\right).3.3.8}{5.3.2.7.4.3}\)
\(=\frac{-16}{7}\)
b) \(\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{15}{21}.\frac{4}{\left(-5\right)}\)
\(=\frac{7}{3}.\frac{\left(-5\right)}{2}.\frac{5}{7}.\frac{2.2}{\left(-5\right)}\)
\(=\frac{7.\left(-5\right).5.2.2}{3.2.7.\left(-5\right)}\)
\(=\frac{10}{3}\)
Bài 2:
a) \(\frac{21}{24}.\frac{11}{9}.\frac{5}{7}=\frac{7}{8}.\frac{11}{9}.\frac{5}{7}=\frac{11.5}{8.9}=\frac{55}{72}\)
b) \(\frac{5}{23}.\frac{17}{26}+\frac{5}{23}.\frac{9}{26}\)
\(=\frac{5}{23}.\left(\frac{17}{26}+\frac{9}{26}\right)=\frac{5}{23}.1=\frac{5}{23}\)
c) \(\left(\frac{3}{29}-\frac{1}{5}\right).\frac{29}{3}=\frac{3}{29}.\frac{29}{3}-\frac{1}{5}.\frac{29}{3}\)
\(=1-1\frac{14}{15}=\frac{14}{15}\)
Bài 3:
a) x/5 = 2/5
=> x =2
b) -4/x = 20/14 = 10/7
=> -4/x = 10/7
=> x.10 = (-4).7
x.10 = - 28
x= -28 :10
x= -2,8
c) 4/7 = 12/x = 12/ 21
=> 12/x = 12/21
=> x = 21
d) 3/7 = x / 21 = 9/21
=> x/21 = 9/21
=> x= 9
![](https://rs.olm.vn/images/avt/0.png?1311)
a: =30-22=8
b: =10*(23+17)=10*40=400
c: =21*3-7*(-14)
=63+98=161
d: =-20-[10*10*5^2+16]
=-20-100*25-16
=-36-2500
=-2536
![](https://rs.olm.vn/images/avt/0.png?1311)
\(x:x-54\cdot17\cdot\frac{6}{17}\cdot3\cdot4=12\)
\(x:x=12+\left(54\cdot17\cdot\frac{6}{17}\cdot3\cdot4\right)\)
x:x = ?
còn lại lm giúp mk nhá +0
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 6:
\(21,251+6,058+0,749+1,042\)
\(=\left(21,251+0,749\right)+\left(6,058+1,042\right)\)
\(=22+7,1\)
\(=29,1\)
___________________
\(1,53+5,309+12,47+5,691\)
\(=\left(1,53+12,47\right)+\left(5,309+5,691\right)\)
\(=14+11\)
\(=25\)
5:
a: =>x/17=5/17
=>x=5
b; =>6+x=7/11*33=21
=>x=15
c: \(\dfrac{12+x}{43-x}=\dfrac{2}{3}\)
=>3x+36=86-2x
=>5x=50
=>x=10
d: \(\dfrac{x}{5}< \dfrac{3}{7}\)
=>x<3/7*5
=>x<15/7
f: 15/26+x/16=46/52
=>x/16=23/26-15/26=8/26=4/13
=>x=4/13*16=64/13
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{4}{x}=\dfrac{y}{21}=\dfrac{28}{49}=\dfrac{28:7}{49:7}=\dfrac{4}{9}\\ Vậy:x=\dfrac{4.9}{4}=9\\ y=\dfrac{4.21}{9}=\dfrac{28}{3}\)
\(\dfrac{x}{2}=\dfrac{3}{y}\\ \Leftrightarrow x.y=2.3=6\\ Vậy:\left[{}\begin{matrix}\left(x;y\right)=\left(1;6\right)=\left(6;1\right)\\\left(x;y\right)=\left(2;3\right)=\left(3;2\right)\end{matrix}\right.\)
Bài 2:
a) 37 x 7 - 17 x 11 + 13 x 37 + 17 x 21
b) 55 x 52 : 54 - 28 : 24
c) 311 x 12 + 312 x 5 - 314
![](https://rs.olm.vn/images/avt/0.png?1311)
`#040911`
`a)`
\(37 \times 7 - 17 \times 11 + 13 \times 37 + 17 \times 21\)
`= 37 \times (7 + 13) + 17 \times (21 - 11)`
`= 37 \times 20 + 17 \times 10`
`= 10 \times (37 \times 2 + 17)`
`= 10 \times 91`
`= 910`
`b)`
\(5^5 \times 5^2 \div 5^4 - 2^8 \div 2^4\)
`=`\(5^{5+2-4}-2^{8-4}\)
`= 5^3 - 2^4`
`= 125 - 16`
`= 109`
`c)`
\(3^{11}\times12+3^{12}\times5-3^{14}\)
`=`\(3^{11}\times\left(12+3\times5-3^3\right)\)
`=`\(3^{11}\times\left(12+15-27\right)\)
`=`\(3^{11}\times0=0\)
a) = 259 - 187 + 481 + 357
= 910
b) = 57 : 54 - 24
= 53 - 24
= 125 - 16
= 109
4.x-54:17=21
4x=21+(54/17)
4x=411/17
x=(411/17):4
x=411/68
ngày 1 bán 3/8 tấm vải.
ngày 2 bán 2/5 tấm vải
phần vải ngày 2 nhiều hơn ngày 1 4,5m
sau 2 ngày còn lại m vải