a)3^x+1=9^x
3^x+1=3.3^x
3^x+1=3^x+1
=>x thuộc TH Z
b)2^3.x+2=4^x+5
2^3x+2=2^2.(x+5)
2^3x+2=2^2x+10
2^3x=2^2x+8
3x-2x=8
=>x=8
c)3^2x-1=243
3^2x=243.3
3^2x=729
3^2x=3^6
=>2x=6
x=6:2=3
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\(3^{x+1}=9^x\)
=>: \(3^{x+1}=\left(3^2\right)^x\)
=> \(3^{x+1}=3^{2x}\)
=> x + 1 = 2x
=> 1 = 2x - x
=> x =1
b, \(2^{3x+2}=4^{x+5}\)
=> \(2^{3x+2}=\left(2^2\right)^{x+5}\)
=> \(2^{3x+2}=2^{2.\left(x+5\right)}\)
=> 3x + 2 = 2,.(x + 5)
=> 3x +2 = 2x + 10
=> 2 - 10 = 2x - 3x
=> -8 = -x
=> x = 8
c, \(3^{2x-1}=243\)
=> \(3^{2x+1}=3^5\)
=> 2x + 1 = 5
=> 2x = 4
=> x = 4 : 2
=. x = 2
