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\(\dfrac{7^x}{7^2}=343\)
\(\Rightarrow7^{x-2}=343\)
\(\Rightarrow7^{x-2}=7^3\)
\(\Rightarrow x-2=3\)
\(\Rightarrow x=3+2\)
\(\Rightarrow x=5\)
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Giúp tôi giải toán - Hỏi đáp, thảo luận về toán học - Học toán với OnlineMath
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a) \(3^x=27=3^3\)
=> x= 3
b) \(5^x=125=5^3\)
=> x = 3
c) \(2^x.2^3=2^{64}\)
\(2^{x+3}=2^6\)
=> x+ 3 = 6
=> x = 6 - 3
=> x = 3
d) \(7.7^{x+2}=343\)
\(7^{x+3}=7^3\)
=> x + 3 = 3
=> x = 0
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\(\Rightarrow x-72-18=-12\\ \Rightarrow x-90=-12\\ \Rightarrow x=-78\)
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a/2x+2-2x=96
2x(22-1)=96
2x3=96
2x=96:3
2x=32
2x=25
x=5
b/(x-1)3=125
(x-1)3=53
x-1=5
x=6
c/(2x+1)3=343
(2x+1)3=73
2x+1=7
2x=6
x=3
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4 . x3 + 15 = 47
4 . x3 = 47 - 15
4 . x3 = 32
x3 = 32 : 4
x3 = 8
=> x = 2
4 . 2x - 3 = 125
4 . 2x = 125 + 3
4 . 2x = 128
2x = 128 : 4
2x = 32
=> x = 5
\(x+72=125-343\)
\(\Rightarrow x+72=-218\)
\(\Rightarrow x=-290\)(thỏa mãn)