5^x+4-3.5^x-3+2.5^11
Tìm x
5^x+4-3.5^x+3=2.5^11
\(\Leftrightarrow5^x\cdot625-3\cdot5^x\cdot125=2\cdot5^{11}\)
\(\Leftrightarrow5^x\cdot250=2\cdot5^{11}\)
\(\Leftrightarrow5^x=5^8\)
hay x=8
5^(x+4) -3.5^(x+3)=2.5^1
Ta có:\(5^{x+4}-3\cdot5^{x+3}=2\cdot5\)
\(5^x\cdot5^4-3\cdot5^x\cdot5^3=10\)
\(5^x\left(5^4-3\cdot5^3\right)=10\)
\(5^x\cdot250=10\)
\(5^x=10:250\)
\(5^x=\frac{1}{25}\)
\(5^x=5^{-2}\)
\(\Rightarrow x=-2\)
\(5^{x+4}-3.5^{x+3}=2.5\)
\(\Rightarrow5^{x+3}.5-3.5^{x+3}=2.5\)
\(\Rightarrow5^{x+3}.\left(5-3\right)=2.5\)
\(\Rightarrow5^{x+3}.2=2.5\)
\(\Rightarrow5^{x+3}=5\)
\(\Rightarrow x+3=1\)
\(\Rightarrow x=-2\)
Vậy \(x=-2\)
5^x+4-3.5^x-3=2.5^11
5^x+4-3.5^x-3=2.5^11
5^x+4-3.5^x-3+2.5^11
5^x+4-3.5^x-3=2.5^11
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\(5^{x+4}-3.5^{x+3}=2.5^{11}\)
\(5^{x+4}-3.5^{x+3}=2.5^{11}\)
\(\Rightarrow5^x.5^4-3.5^x.5^3=2.5^{11}\)
\(\Rightarrow5^x.5^3\left(5-3\right)=2.5^{11}\)
\(\Rightarrow5^x.2=2.5^8\)
\(\Rightarrow5^x=5^8\)
\(\Rightarrow x=8\)
Vậy \(x=8\)
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Bài 6: 1) 3^x+2+4.3^x+1=7.3^6 2)5^x+4-3.5^x+3=2.5^11 3)4^x+3-3.4^x+1=13.4^11
Lời giải:
1.
$3^{x+2}+4.3^{x+1}=7.3^6$
$3^{x+1}.3+4.3^{x+1}=7.3^6$
$3^{x+1}(3+4)=7.3^6$
$3^{x+1}.7=7.3^6$
$\Rightarrow 3^{x+1}=3^6$
$\Rightarrow x+1=6$
$\Rightarrow x=5$
2.
$5^{x+4}-3.5^{x+3}=2.5^{11}$
$5^{x+3}.5-3.5^{x+3}=2.5^{11}$
$5^{x+3}(5-3)=2.5^{11}$
$2.5^{x+3}=2.5^{11}$
$\Rightarrow 5^{x+3}=5^{11}$
$\Rightarrow x+3=11$
$\Rightarrow x=8$
3.
$4^{x+3}-3.4^{x+1}=13.4^{11}$
$4^{x+1}.4^2-3.4^{x+1}=13.4^{11}$
$4^{x+1}.16-3.4^{x+1}=13.4^{11}$
$13.4^{x+1}=13.4^{11}$
$\Rightarrow 4^{x+1}=4^{11}$
$\Rightarrow x+1=11$
$\Rightarrow x=10$
5x+4-3.5x+3=2.511