tìm số tự nhiên x , biết :
1) 58 + 7x=100
2)(x-12):12=12
3)x-56:4=16
4) 101+(36-4x)=105
5)2(x-51)=2.2 mũ 3 + 20
dạng bài khá khó nên cẩn thân khi làm nha ^-^
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a: 7x+58=100
nên 7x=42
hay x=6
c: x-56:x=16
nên x-14=16
hay x=30
c)x - 56 : 4 = 16
x - 56 = 16 : 4
x- 56 = 4
x =4 + 56
x = 60
d)101 + (36 - 4x) = 105
(36- 4x ) = 105 - 101
36 - 4x = 4
4x = 36 - 4
4x = 32
x = 32:4
x = 8
\(1,\Leftrightarrow7x=42\Leftrightarrow x=6\\ 2,\Leftrightarrow36-4x=4\Leftrightarrow4x=32\Leftrightarrow x=8\\ 3,\Leftrightarrow3x=35\Leftrightarrow x=\dfrac{35}{3}\\ 4,\Leftrightarrow x-12=144\Leftrightarrow x=156\\ 5,\Leftrightarrow x-14=16\Leftrightarrow x=30\\ 6,\Leftrightarrow3x-24=\dfrac{148}{73}\Leftrightarrow3x=\dfrac{1900}{73}\Leftrightarrow x=\dfrac{1900}{219}\\ 7,\Leftrightarrow33+x=45\Leftrightarrow x=12\\ 8,Sai.đề\\ 9,\Leftrightarrow\left(x+9\right):2=39\Leftrightarrow x+9=78\Leftrightarrow x=69\\ 11,\Leftrightarrow2\left(x+7\right)=38\Leftrightarrow x+7=19\Leftrightarrow x=12\\ 13,\Leftrightarrow2\left(x-51\right)=66\Leftrightarrow x-51=33\Leftrightarrow x=84\)
\(15,\Leftrightarrow x-19=9\Leftrightarrow x=28\\ 17,\Leftrightarrow\left(x-3\right):2=48\Leftrightarrow x-3=96\Leftrightarrow x=99\\ 19,\Leftrightarrow0x=46\Leftrightarrow x\in\varnothing\\ 8,Sai.đề\\ 14,\Leftrightarrow2x=209\Leftrightarrow x=\dfrac{209}{2}\\ 16,\Leftrightarrow2x+6=157\Leftrightarrow2x=151\Leftrightarrow x=\dfrac{151}{2}\\ 18,\Leftrightarrow5\left(x+4\right)=100\Leftrightarrow x+4=20\Leftrightarrow x=16\\ 20,\Leftrightarrow\left(3x-5\right)^3=27=3^3\Leftrightarrow3x-5=3\Leftrightarrow x=\dfrac{8}{3}\)
a) \(58+7x=100\)
\(=>7x=100-58\)
\(=>7x=42\)
\(=>x=42:7\)
\(=>x=6\)
b) \(3x-7=28\)
\(=>3x=28+7\)
\(=>3x=35\)
\(=>x=35:3\)
\(=>x=\dfrac{35}{3}\)
c) \(x-56:4=16\)
\(=>x-14=16\)
\(=>x=16+14\)
\(=>x=30\)
d) \(101+\left(36-4x\right)=105\)
\(=>36-4x=105-101\)
\(=>36-4x=4\)
\(=>4x=36-4\)
\(=>4x=32\)
\(=>x=32:4\)
\(=>x=8\)
e) \(\left(x-12\right):12=12\)
\(=>x-12=12.12\)
\(=>x-12=144\)
\(=>x=144-12\)
\(=>x=132\)
f) \(\left(3x-2^4\right).7^3=2.7^4\)
\(=>3x-2^4=2.7^4:7^3\)
\(=>3x-16=2.7=14\)
\(=>3x=14+16\)
\(=>3x=30\)
\(=>x=30:3\)
\(=>x=10\)
i) \(\left(10+2x\right).4^{2011}=4^{2013}\)
\(=>10+2x=4^{2013}:4^{2011}\)
\(=>10+2x=4^2=16\)
\(=>2x=16-10\)
\(=>2x=6\)
\(=>x=6:2\)
\(=>x=3\)
\(#WendyDang\)
a: =>7x=42
hay x=6
b: =>5x=35
hay x=7
c: =>x-14=16
hay x=30
d: =>36-4x=4
=>4x=32
hay x=8
e: =>x-12=144
hay x=156
f: =>3x-16=14
hay x=10
g: =>x+33=45
hay x=12
h: =>(x+9):2=39
=>x+9=78
hay x=69
a: =>7x=42
hay x=6
b: =>5x=35
hay x=7
c: =>x-14=16
hay x=30
d: =>36-4x=4
=>4x=32
a: x-56:4=16
nên x-14=16
hay x=30
b: \(101+\left(36-4x\right)=105\)
\(\Leftrightarrow36-4x=4\)
hay x=8
Vì a: x-56:4=16
=>x-14=16
Hay:x=30
Vì b: 101+(36−4x)=105101+(36−4x)=105
⇔36−4x=4⇔36−4x=4
Hay:x=8
Vậy x={30:8}
Nếu sai thì thui nhá,đừng chửi mình!
Bài 6 :
a) \(\dfrac{625}{5^n}=5\Rightarrow\dfrac{5^4}{5^n}=5\Rightarrow5^{4-n}=5^1\Rightarrow4-n=1\Rightarrow n=3\)
b) \(\dfrac{\left(-3\right)^n}{27}=-9\Rightarrow\dfrac{\left(-3\right)^n}{\left(-3\right)^3}=\left(-3\right)^2\Rightarrow\left(-3\right)^{n-3}=\left(-3\right)^2\Rightarrow n-3=2\Rightarrow n=5\)
c) \(3^n.2^n=36\Rightarrow\left(2.3\right)^n=6^2\Rightarrow\left(6\right)^n=6^2\Rightarrow n=6\)
d) \(25^{2n}:5^n=125^2\Rightarrow\left(5^2\right)^{2n}:5^n=\left(5^3\right)^2\Rightarrow5^{4n}:5^n=5^6\Rightarrow\Rightarrow5^{3n}=5^6\Rightarrow3n=6\Rightarrow n=3\)
Bài 7 :
a) \(3^x+3^{x+2}=9^{17}+27^{12}\)
\(\Rightarrow3^x\left(1+3^2\right)=\left(3^2\right)^{17}+\left(3^3\right)^{12}\)
\(\Rightarrow10.3^x=3^{34}+3^{36}\)
\(\Rightarrow10.3^x=3^{34}\left(1+3^2\right)=10.3^{34}\)
\(\Rightarrow3^x=3^{34}\Rightarrow x=34\)
b) \(5^{x+1}-5^x=100.25^{29}\Rightarrow5^x\left(5-1\right)=4.5^2.\left(5^2\right)^{29}\)
\(\Rightarrow4.5^x=4.25^{2.29+2}=4.5^{60}\)
\(\Rightarrow5^x=5^{60}\Rightarrow x=60\)
c) Bài C bạn xem lại đề
d) \(\dfrac{3}{2.4^x}+\dfrac{5}{3.4^{x+2}}=\dfrac{3}{2.4^8}+\dfrac{5}{3.4^{10}}\)
\(\Rightarrow\dfrac{3}{2.4^x}-\dfrac{3}{2.4^8}+\dfrac{5}{3.4^{x+2}}-\dfrac{5}{3.4^{10}}=0\)
\(\Rightarrow\dfrac{3}{2}\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)+\dfrac{5}{3.4^2}\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)=0\)
\(\Rightarrow\left(\dfrac{1}{4^x}-\dfrac{1}{4^8}\right)\left(\dfrac{3}{2}+\dfrac{5}{3.4^2}\right)=0\)
\(\Rightarrow\dfrac{1}{4^x}-\dfrac{1}{4^8}=0\)
\(\Rightarrow\dfrac{4^8-4^x}{4^{x+8}}=0\Rightarrow4^8-4^x=0\left(4^{x+8}>0\right)\Rightarrow4^x=4^8\Rightarrow x=8\)
Bài 9,
62x73+36x33=36x73+36x27=36(73+27)=36x100=3600.
197-\([\)6x(5-1)2+20220\(]\):5=197-\([\)6x16+1\(]\):5=197-97:5=197-97/5=888/5.
Bài 10,
21-4x=13
=>4x=21-13=8
=>x=8:4=2.
30:(x-3)+1=45:43=42=16
=>30:(x-3)=16-1=15
=>x-3=30:15=2
=>x=2+3=5.
(x-1)3+5x6=38
=>(x-1)3+30=38
=>(x-1)3=38-30=8=23
=>x-1=2
=>x=3.
a. 348 : x = 12
x = 348 : 12
x = 29
b. 9x - 7 = 119
9x = 119 + 7
9x = 126
x = 126 : 9
x = 14
c. 100 - 7 . ( x - 5 ) = 58
7 . ( x - 5 ) = 100 - 58
7 . ( x - 5 ) = 42
x - 5 = 42 : 7
x - 5 = 6
x = 6 + 5
x = 11
d. x không thuộc số tự nhiên
a)348:x=12
x=348:12
x=29
b)9x-7=119
9x=119+7
9x=126
x=126:9
x=14
c)100-7.(x-5)=58
7.(x-5)=100-58
7.(x-5)=42
x-5=42:7
x-5=6
x=6+5
x=11
d)2x-2.23=64
2x-2.8=64
2x-16=64
2x=64+16
2x=80
đề sai
`#3107.101107`
`1)`
`58 + 7x = 100`
`=> 7x = 100 - 58`
`=> 7x = 42`
`=> x = 42 \div 7`
`=> x = 6`
Vậy, `x = 6`
`2)`
`(x - 12) \div 12 = 12`
`=> x - 12 = 12*12`
`=> x - 12 = 144`
`=> x = 144 + 12`
`=> x = 156`
Vậy, `x = 156`
`3)`
`x - 56 \div 4 = 16`
`=> x - 14 = 16`
`=> x = 16 + 14`
`=> x = 30`
Vậy, `x = 30`
`4)`
`101 + (36 - 4x) = 105`
`=> 36 - 4x = 105 - 101`
`=> 36 - 4x = 4`
`=> 4x = 36 - 4`
`=> 4x = 32`
`=> x = 32 \div 4`
`=> x = 8`
Vậy, `x = 8`
`5)`
`2(x - 51) = 2*2^3 + 20`
`=> 2(x - 51) = 2^4 + 20`
`=> 2(x - 51) = 16 + 20`
`=> 2(x - 51) = 36`
`=> x - 51 = 36 \div 2`
`=> x - 51 = 18`
`=> x = 18 + 51`
`=> x = 69`
Vậy, `x = 69.`
1) 58 + 7x=100
7x = 100 - 58
7x = 42
x = 42 : 7
x = 6
2)(x-12):12=12
(x - 12) = 12 x 12
x - 12 = 144
x = 144 + 12
x = 156
3)x-56:4=16
x - 14 = 16
x = 16 + 14
x = 30
4) 101+(36-4x)=105
(36-4x) = 105 - 101
36-4x = 4
4x = 36 - 4
4x = 32
x = 32 : 4
x = 8
5)2(x-51)=2.2 mũ 3 + 20
2(x-51)=2.8 + 20
2(x-51)=16 + 20
2(x-51)= 36
x - 51 = 36 : 2
x - 51 = 18
x = 18 + 51
x = 69