5.2mũ3 7mũ11:7mũ9-1 mũ 8
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Bài 1:
2\(x\) = 4
2\(^x\) = 22
\(x=2\)
Vậy \(x=2\)
Bài 2:
2\(^x\) = 8
2\(^x\) = 23
\(x=3\)
Vậy \(x=3\)
a) Ta có :
\(27^{27}>27^{26}=\left(27^2\right)^{13}=729^{13}>243^{13}\)
\(\Rightarrow27^{27}>243^{13}\)
\(\Rightarrow-27^{27}< -243^{13}\)
\(\Rightarrow\left(-27\right)^{27}< \left(-243\right)^{13}\)
b) \(\left(\dfrac{1}{8}\right)^{25}>\left(\dfrac{1}{8}\right)^{26}=\left(\dfrac{1}{8^2}\right)^{13}=\left(\dfrac{1}{64}\right)^{13}>\left(\dfrac{1}{128}\right)^{13}\)
\(\Rightarrow\left(\dfrac{1}{8}\right)^{25}>\left(\dfrac{1}{128}\right)^{13}\)
\(\Rightarrow\left(-\dfrac{1}{8}\right)^{25}< \left(-\dfrac{1}{128}\right)^{13}\)
c) \(4^{50}=\left(4^5\right)^{10}=1024^{10}\)
\(8^{30}=\left(8^3\right)^{10}=512^{10}< 1024^{10}\)
\(\Rightarrow4^{50}>8^{30}\)
d) \(\left(\dfrac{1}{9}\right)^{17}< \left(\dfrac{1}{9}\right)^{12}< \left(\dfrac{1}{27}\right)^{12}\)
\(\Rightarrow\left(\dfrac{1}{9}\right)^{17}< \left(\dfrac{1}{27}\right)^{12}\)
a) Ta có :
2727>2726=(272)13=72913>243132727>2726=(272)13=72913>24313
⇒2727>24313⇒2727>24313
⇒−2727<−24313⇒−2727<−24313
⇒(−27)27<(−243)13⇒(−27)27<(−243)13
b) (18)25>(18)26=(182)13=(164)13>(1128)13(81)25>(81)26=(821)13=(641)13>(1281)13
⇒(18)25>(1128)13⇒(81)25>(1281)13
⇒(−18)25<(−1128)13⇒(−81)25<(−1281)13
c) 450=(45)10=102410450=(45)10=102410
830=(83)10=51210<102410830=(83)10=51210<102410
⇒450>830⇒450>830
d) (19)17<(19)12<(127)12(91)17<(91)12<(271)12
⇒(19)17<(127)12⇒(91)17<(271)12
\(\left(3x-8\right)^{10}=\left(3x-8\right)^2\\ \Rightarrow\left(3x-8\right)^{10}-\left(3x-8\right)^2=0\\ \Rightarrow\left(3x-8\right)^2\left[\left(3x-8\right)^8-1\right]=0\\ \Rightarrow\left[{}\begin{matrix}\left(3x-8\right)^2=0\\\left(3x-8\right)^8=1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}3x-8=0\\3x-8=1\\3x-8=-1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=\dfrac{8}{3}\\x=3\\x=\dfrac{7}{3}\end{matrix}\right.\)
\(243\le3^{2x-1}\le3^8\\ \Rightarrow3^5\le3^{2x-1}\le3^8\\ \Rightarrow2x-1\in\left\{5;6;7;8\right\}\\ \Rightarrow x\in\left\{3;\dfrac{7}{2};4;\dfrac{9}{2}\right\}\)
\(=5\cdot8+7^2-1=40+49-1=88\)
\(=5\cdot8+7^2-1=40+49-1=88\)