Tìm số tự nhiên x:
a) \(\frac{1}{27}\). 9x= 3x
b) 2x-1+ 5 .2x-2 =\(\frac{7}{32}\)
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26 tháng 12 2021
\(a.12+2x=6^3:6^2\\ 12+2x=6\\ 2x=12-6\\ 2x=6\\ x=6:2\\ x=3\)
\(b.48:x+17=33\\ 48:x=33-17\\ 48:x=16\\ x=48:16\\ x=3\)
\(c.\left(9x+2\right).5+28=83\\ \left(9x+2\right).5=83-28\\ \left(9x+2\right).5=55\\ 9x+2=55:5\\ 9x+2=11\\ 9x=11-2\\ 9x=9\\ x=9:9\\ x=1\)
\(d.187-2.\left(x+5\right)=125\\ 2.\left(x+5\right)=187-125\\ 2.\left(x+5\right)=62\\ x+5=62:2\\ x+5=31\\ x=31-5\\ x=26\)
19 tháng 7 2017
\(5^{x+2}+5^{x+3}=750\)
\(5^x.5^2+5^x.5^3=750\)
\(5^x.25+5^x\cdot125=750\)
\(5^x.\left(25+125\right)=750\)
\(5^x.150=750\)
\(5^x=750:150\)
\(5^x=5\)
\(5^x=5^1\)
\(\Rightarrow x=1\)
20 tháng 10 2021
a) \(2^x:4=16\\ \Rightarrow2^x=64\\ \Rightarrow2^x=2^6\\ \Rightarrow x=6\)
b) \(4^{x-3}=256\\ \Rightarrow4^{x-3}=4^4\\ \Rightarrow x-3=4\\ \Rightarrow x=7\)
c) \(\left(2x+1\right)^3=343\\ \Rightarrow\left(2x+1\right)^3=7^3\\ \Rightarrow2x+1=7\\ \Rightarrow x=3\)
d) \(10+2x=4^5:4^3\\ \Rightarrow10+2x=16\\ \Rightarrow x=3\)
20 tháng 10 2021
a,2^x:4=16
2^x=16.4=64
2^x=2^6
=>x=6
b,4^x-3=256
4^x-3=4^4
=>x-3=4
x=4+3=7
c,(2x+1)^3=343
(2x+1)^3=7^3
=>2x+1=7
2x=7-1=6
x=6:2=3
d,10+2x=4^5:4^3
10+2x=4^2=16
2x=16-10=6
x=6:2=3
LN
20 tháng 10 2021
a, 2x : 4 = 16
⇒ 2x : 22 = 24
⇒ x - 2 = 4
⇒ x = 6
b, 4x-3 = 256
⇒ 4x - 3 = 44
⇒ x - 3 = 4
⇒ x = 7
c, (2x + 1)3 = 343
⇒ (2x + 1)3 = 73
⇒ 2x + 1 = 7
⇒ 2x = 6
⇒ x = 3
d, 10 + 2x = 45 : 43
⇒ 10 + 2x = 16
⇒ 2x = 6
⇒ x = 3
NT
6 tháng 8 2019
\(\frac{2x+3}{2x+1}-\frac{2x+5}{2x+7}=1-\frac{6x^2+9x-9}{\left(2x+1\right)\left(2x+7\right)}\)
\(\Leftrightarrow1+\frac{2}{2x+1}-1-\frac{2}{2x+7}-1=-\frac{6x^2+9x-9}{\left(2x+1\right)\left(2x+7\right)}\)
\(\Leftrightarrow\frac{4x+14-4x-2+6x^2+9x-9}{\left(2x+1\right)\left(2x+7\right)}=1\)
\(\Leftrightarrow\frac{6x^2+9x+3}{\left(2x+1\right)\left(2x+7\right)}=1\)
\(\Leftrightarrow\frac{6x^2+6x+3x+3}{\left(2x+1\right)\left(2x+7\right)}=1\)
\(\Leftrightarrow\frac{6x\left(x+1\right)+3\left(x+1\right)}{\left(2x+1\right)\left(2x+7\right)}=1\)
\(\Leftrightarrow\frac{3\left(2x+1\right)\left(x+1\right)}{\left(2x+1\right)\left(2x+7\right)}=1\)
\(\Leftrightarrow3x+3=2x+7\)
\(\Leftrightarrow x=4\)
C
1
7 tháng 7 2021
\(a,\left(3x-7\right)^2=\left(2-2x\right)^2\)
a,\(=>\left(3x-7\right)^2-\left(2-2x\right)^2=0\)
\(< =>\left(3x-7+2-2x\right)\left(3x-7-2+2x\right)=0\)
\(< =>\left(x-5\right)\left(5x-9\right)=0=>\left[{}\begin{matrix}x=5\\x=1,8\end{matrix}\right.\)
b, \(x^2-8x+6=0< =>x^2-2.4x+16-10=0\)
\(< =>\left(x-4\right)^2-\sqrt{10}^2=0\)
\(=>\left(x-4+\sqrt{10}\right)\left(x-4-\sqrt{10}\right)=0\)
\(=>\left[{}\begin{matrix}x=4-\sqrt{10}\\x=4+\sqrt{10}\end{matrix}\right.\)
c, \(4x^2-2x-1=0\)
\(< =>\left(2x\right)^2-2.2.\dfrac{1}{2}x+\dfrac{1}{4}-\dfrac{5}{4}=0\)
\(=>\left(2x-\dfrac{1}{2}\right)^2-\left(\dfrac{\sqrt{5}}{2}\right)^2=0\)
\(=>\left(2x+\dfrac{-1+\sqrt{5}}{2}\right)\left(2x-\dfrac{1+\sqrt{5}}{2}\right)=0\)
\(=>\left[{}\begin{matrix}x=\dfrac{1-\sqrt{5}}{4}\\x=\dfrac{1+\sqrt{5}}{4}\end{matrix}\right.\)
d,\(x^4-4x^2-32=0\)
đặt \(t=x^2\left(t\ge0\right)=>t^2-4t-32=0\)
\(< =>t^2-2.2t+4-6^2=0\)
\(=>\left(t-2\right)^2-6^2=0=>\left(t-8\right)\left(t+4\right)=0\)
\(=>\left[{}\begin{matrix}t=8\left(tm\right)\\t=-4\left(loai\right)\end{matrix}\right.\)\(=>x=\pm\sqrt{8}\)
17 tháng 8 2017
Tìm số tự nhiên x: \(2^{x-1}+5.2^{x-2}=224\Leftrightarrow2.2^{x-2}+5.2^{x-2}=224\)
\(\Leftrightarrow2^{x-2}.\left(5+2\right)=224\Leftrightarrow2^{x-2}.7=224\)
\(\Rightarrow2^{x-2}=32\Leftrightarrow2^{x-2}=2^5\)\(\Rightarrow x-2=5\Leftrightarrow x=7\)
Vậy x=7
Tìm x biết: \(\frac{3}{7}=\frac{2x+1}{3x+5}\)
\(\Rightarrow3\left(3x+5\right)=7\left(2x+1\right)\Leftrightarrow9x+15=14x+7\)
\(\Leftrightarrow14x+7-\left(9x+15\right)=0\Rightarrow5x+\left(-8\right)=0\)
\(\Leftrightarrow5x=8\Rightarrow x=\frac{8}{5}\)
Vậy x=8/5
16 tháng 6 2023
`@` `\text {Ans}`
`\downarrow`
`a)`
`3x ( 12x - 4 ) - 9x( 4x - 3 ) = 30`
`=> 3x (12x-4) - 3*3x (4x - 3) = 30`
`=> 3x [12x - 4 - 3(4x-3)] = 30`
`=> 3x (12x - 4 - 12x + 9) = 30`
`=> 3x (-4+9)=30`
`=> 3x*5=30`
`=> 3x=6`
`=> x=2`
Vậy, `x=2`
`b)`
`x( 5 - 2x) + 2x( x - 1)`
`=> x(5-2x) + 2x^2 - 2x=15`
`=> 5x - 2x^2 + 2x^2 - 2x =15`
`=> 3x = 15`
`=> x=5`
Vậy, `x=5.`
16 tháng 6 2023
a: =>36x^2-12x-36x^2+27x=30
=>15x=30
=>x=2
b: =>5x-2x^2+2x^2-2x=15
=>3x=15
=>x=5
A)=3
B)=-3
CAU THAY SO NHA