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a. 3^x=1-x^2
x=0 la nghiem
x>=1; VT>=3 VP<=0 vo nghiem
b. (de bai thieu n khac 0 vi neu n=0 dung voi moi x)
3x-14=1=> x=5
c.(5^2x5^x+1)=5^4
5^x+1=5^2=> x=1
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\(\Rightarrow-3x=\dfrac{6}{7}-\dfrac{30}{21}\\ \Rightarrow-3x=\dfrac{18}{21}-\dfrac{30}{21}\\\Rightarrow-3x=\dfrac{-12}{21}\\ \Rightarrow x=\dfrac{-12}{21}:3\\ \Rightarrow x=\dfrac{-12}{63}=\dfrac{-4}{21} \)
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3x + 3x+1 + 3x+2 = 243 . 39
3x.(1+3+9) = 36 . 13
3x . 13 = 36 . 13
=> x = 13
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+) x3 : 2 = 4
x3 = 4 . 2 = 8
x3 = 23
=> x = 2
+) 5x-2 = 1
=> 5x : 52 = 1
=> 5x = 52
=> x = 2
+) 3x + 3x+1 + 3x+2 = 243 . 39
3x + 3x . 3 + 3x . 32 = 9477
3x . (1+3+ 32) = 9477
3x . 13 = 9477
3x = \(\frac{9477}{13}\) = 729
3x = 36
=> x = 6
x3:2=4
\(\Rightarrow\)x3=4.2
\(\Rightarrow\)x3=8
\(\Rightarrow\)x3=23
\(\Rightarrow\)x=2
Vậy:x=2
5x-2=1
\(\Rightarrow\)5x-2=50
\(\Rightarrow\)x-2=0
\(\Rightarrow\)x=2
Vậy:x=2
3x+3x+1+3x+2=243.39
\(\Rightarrow\)3x+3x+1+3x+2=9477
\(\Rightarrow\)3x+3x.3+3x.32=9477
\(\Rightarrow\)3x=9477:13
\(\Rightarrow\)3x=729
\(\Rightarrow\)3x=36
\(\Rightarrow\)x=6
Vậy:x=6
![](https://rs.olm.vn/images/avt/0.png?1311)
$\Rightarrow 3^x(1+3+3^2+3^3)=1080$
$\Rightarrow 3^x.40=1080$
$\Rightarrow 3^x=27=3^3$
$\Rightarrow x=3$
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\(3^x+3^{x+1}+3^{x+2}=117\)
\(3^x+3^x.3+3^x.3^2=117\)
\(3^x\left(1+3+3^2\right)=117\)
\(3^x.13=117\)
\(3^x=9\)
\(\Rightarrow x=2\)
\(3^x+3^{x+1}+3^{x+2}=243.39\)
\(3^x.\left(1+3^1+3^2\right)=243.3.13\)
\(3^x.\left(1+3+9\right)=\left(243.3\right).13\)
\(3^x.13=729.13\)
\(3^x=729.13\div13\)
\(3^x=729\)
\(3^x=3^6\)
\(x=6\)
\(3^x+3^{x+1}+3^{x+2}=243.39\)
\(\Leftrightarrow3^x+3^x.3+3^x.3^2=9477\)
\(\Leftrightarrow3^x\left(1+3+3^2\right)=9477\)
\(\Leftrightarrow3^x.13=9477\)
\(\Leftrightarrow3^x=9477:13\)
\(\Leftrightarrow3^x=729\)
\(\Leftrightarrow3^x=3^6\)
\(\Leftrightarrow x=6\)
~ Rất vui vì giúp đc bn ~