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Bài 3:
Gọi x thuộc N* số học sinh lớp 6a
Theo đề ta có
x:3
x:4
x:8
40<x<50
Suy ra x thuộc BC(3;4;8)
4=2^2
8=2^3
BCNN(3;4;8)=3.2^3=24
BC(3;4;8)=B(24)={0;24;48;72;...}
Mà 40<x<50
Suy ra x=48
Vậy lớp 6a có 48 Học sinh
(Có thể thay thế x bằng chữ cái khác.Chúc bn học tốt :3)
\(\left(17x-25\right):8+65=9^2\)
=> \(\frac{17x}{8}-\frac{25}{8}+65=81\)
=> \(\frac{17x}{8}=81-65+\frac{25}{8}\)
=> \(\frac{17x}{8}=\frac{153}{8}\)
=> \(17x=\left(153.8\right):8\)
=> \(17x=153\)
=> \(x=153:17=9\)
(17x - 25 ) : 8 + 65 = 92
(17x - 25 ) : 8 + 65 = 81
(17x - 25) : 8 = 81 - 65 = 16
17x - 25 = 16 x 8 = 128
17x = 128+25=153
x= 153:17 =9
a) (17.x - 25 ) : 8 = 92 : 65= 92/65
17x - 25 = 92/65.8
17x = 2361/65
x= 2361/65 : 17=2361/1105
b) x- 60 = 2017101 - 2017100
x-60 = 2017
x = 2017 + 60
x = 2077
c) 5x . 30-3x.x = 45
5x.3x.x = 45 + 30 = 75
15x.x = 75
a)
5.(12-x)-20=30
⇒60-5x-20=30
⇒-5x=30+20-60
⇒-5x=-10
⇒x=2
b)(17x - 25 ) : 8 + 65 = 92
(17x - 25 ) : 8 + 65 = 81
17x - 25 = 16 x 8 = 128
17x = 128+25=153
x= 153:17 =9
c)
x=23
Giải thích các bước giải:
3x – 10 = 2x + 13
3x-2x=13+10
x=23
d)4(2x+7)-3(3x-2)=24
4.2x+4.7-3.3x+3.2=24
8x+28-9x+6=24
8x-9x=24-28-6=-10
=>(-1)x=-10
x=-10:(-1)
x=10
a. \(5\cdot\left(12-x\right)-20=30\Leftrightarrow5\left(12-x\right)=50\)
\(\Leftrightarrow12-x=50:5=10\)
\(\Leftrightarrow x=12-10=2\)
b. \(\left(17x-25\right):8+65=9^2\)
\(\Leftrightarrow\left(17x-25\right):8=81-65=16\)
\(\Leftrightarrow17x-25=16:8=2\)
\(\Leftrightarrow17x=2+25=27\Leftrightarrow x=\frac{27}{17}\)
c. \(3x-10=2x+13\)
\(\Leftrightarrow3x-2x=10+13\)
\(\Leftrightarrow x=23\)
d. \(4\cdot\left(2x+7\right)-3\cdot\left(3x-2\right)=24\)
\(\Leftrightarrow8x+28-9x+6=24\)
\(\Leftrightarrow34-x=24\Leftrightarrow x=10\)
a) \(8x-40=56\)
\(\Leftrightarrow8x=96\)
\(\Rightarrow x=12\)
b) \(105-3x=60\)
\(\Leftrightarrow3x=45\)
\(\Rightarrow x=15\)
c) \(75883-\left(31200+x\right)=999\)
\(\Leftrightarrow31200+x=74884\)
\(\Rightarrow x=43684\)
d) \(19-9\left(x+1\right)=10\)
\(\Leftrightarrow9\left(x+1\right)=9\)
\(\Leftrightarrow x+1=1\)
\(\Rightarrow x=0\)
e) \(\left(17x-25\right)\div8+65=81\)
\(\Leftrightarrow\left(17x-25\right)\div8=16\)
\(\Leftrightarrow17x-25=128\)
\(\Leftrightarrow17x=153\)
\(\Rightarrow x=9\)
a) 8x - 40 = 56
8x = 56 - 40
8x = 16
x = 2
b) 105 - 3x = 60
3x = 105 - 60
3x = 45
x = 15
c) 75883 - ( 31200 + x ) = 999
75883 - 31200 - x = 999
44683 - x = 999
x = 44683 - 999
x = 43684
d) 19 - 9 ( x + 1 ) = 10
19 - 9x - 9 = 10
10 - 9x = 10
9x = 0
x = 0
e) ( 17x - 25 ) : 8 + 65 = 81
( 17x - 25 ) : 8 = 16
17x - 25 = 128
17x = 128 + 25
17x = 153
x = 9
( 17x - 25 ) : 8 + 65 = 9^2
( 17x - 25 ) : 8 + 65 = 81
( 17x - 25 ) : 8 = 81 - 65
( 17x - 25 ) : 8 = 16
( 17x - 25 ) = 16 x 8
( 17x - 25 ) = 128
17x = 128 + 25
17x = 153
x = 153 : 17
x = 9
\(\left(17x-25\right):8+65=9^2\)
\(\Leftrightarrow\left(17x-25\right):8=81-65\)
\(\Leftrightarrow\left(17x-25\right):8=16\)
\(\Leftrightarrow17x-25=16.8\Leftrightarrow17x=128+25\Leftrightarrow17x=153\Leftrightarrow x=153:17=9\)
(k cho mình với nhá!)
1:
a: \(35\cdot16+35\cdot28-44\cdot15\)
\(=35\left(16+28\right)-44\cdot15\)
\(=44\left(35-15\right)\)
\(=44\cdot20=880\)
b: \(240-2\left(3\cdot5^2-20:2^2\right)\)
\(=240-2\left(3\cdot25-20:4\right)\)
\(=240-150+10=10+90=100\)
2:
b: \(\left(8-3x\right)^4-1=15\)
=>\(\left(3x-8\right)^4=16\)
=>\(\left[{}\begin{matrix}3x-8=2\\3x-8=-2\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=10\\3x=6\end{matrix}\right.\)
=>x=10/3 hoặc x=2
c: \(218-5\left(x-8\right)=2^5:2^2\)
=>\(218-5\left(x-8\right)=2^3=8\)
=>5(x-8)=210
=>x-8=42
=>x=50
d: \(\left(5-3x\right)^4-1=15\)
=>\(\left(3x-5\right)^4-1=15\)
=>\(\left(3x-5\right)^4=16\)
=>\(\left[{}\begin{matrix}3x-5=-4\\3x-5=4\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3x=1\\3x=9\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=3\end{matrix}\right.\)
(17x-25):8+65=92
(17x-25):8 =92-65
(17x-25):8 =27
(17x-25) =\(27\times8\)
(17x-25) =216
17x =216+25
17x =241
x =241:7
x =\(\frac{241}{17}\)
T mk nhé bạn ^...^ ^_^
(17x-25):8+65=92
(17x-25):8=92-65
(17x-25):8=27
(17x-25)=27.8
17x-25=216
17x=216+25
17x=241
x=241:17
x=