PN
2
K
Khách
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24 tháng 7 2017
a) \(3^{x-2}=27\cdot9\)
\(3^{x-2}=3^3\cdot3^2=3^5\)
\(\Rightarrow\)\(x-2=5\Rightarrow x=7\)
b) \(2^{x+1}+2^{x+3}=80\)
\(\Rightarrow2^{x+1}\left(1+2^2\right)=80\)
\(\Rightarrow2^{x+1}\cdot5=80\)
\(\Rightarrow2^{x+1}=16=2^4\)
\(\Rightarrow x+1=4\Rightarrow x=3\)
c) \(2^{2x-3}=16\cdot8\)
\(2^{2x-3}=2^4\cdot2^3=2^7\)
\(\Rightarrow2x-3=7\)
\(\Rightarrow2x=4\Rightarrow x=2\)
d) \(2^{x-2}\cdot2^x=64\)
\(\Rightarrow2^{x-2+x}=64=2^6\)
\(\Rightarrow x-2+x=6\)
\(\Rightarrow2x-2=6\)
\(\Rightarrow2x=8\Rightarrow x=4\)
H
24 tháng 7 2017
Giải:
a) \(3^{x-2}=27.9\)
\(\Leftrightarrow3^{x-2}=3^3.3^2\)
\(\Leftrightarrow3^{x-2}=3^5\)
Vì \(3=3\)
Nên \(x-2=5\)
\(\Leftrightarrow x=5+2\)
\(\Leftrightarrow x=7\)
Vậy x = 7.
b) \(2^{x+1}+2^{x+3}=80\)
\(\Leftrightarrow2^{x+1}\left(1+2^2\right)=80\)
\(\Leftrightarrow2^{x+1}.5=80\)
\(\Leftrightarrow2^{x+1}=\dfrac{80}{5}=16\)
\(\Leftrightarrow2^{x+1}=2^4\)
Vì \(2=2\)
Nên \(x+1=4\)
\(\Leftrightarrow x=4-1\)
\(\Leftrightarrow x=3\)
Vậy x = 3.
c) \(2^{2x-3}=16.8\)
\(\Leftrightarrow2^{2x-3}=2^4.2^3\)
\(\Leftrightarrow2^{2x-3}=2^7\)
Vì \(2=2\)
Nên \(2x-3=7\)
\(\Leftrightarrow2x=7+3=10\)
\(\Leftrightarrow x=\dfrac{10}{2}=5\)
Vậy x = 5.
d) \(2^{x-2}.2^x=64\)
\(2^{2x-2}=2^6\)
Vì \(2=2\)
Nên \(2x-2=6\)
\(\Leftrightarrow2x=6+2=8\)
\(\Leftrightarrow x=\dfrac{8}{2}=4\)
Vậy x = 4.
Chúc bạn học tốt!
BM
4
TV
6 tháng 6 2017
phamthiminhtrang
\(a,x=\frac{3}{6}-\frac{8}{16}\)
\(\Rightarrow x=0\)
\(b,\frac{12}{16}:x=\frac{32}{64}\)
\(x=\frac{12}{16}:\frac{32}{64}\)
\(x=\frac{12}{16}\cdot\frac{64}{32}\)
\(x=\frac{3}{8}\)
6 tháng 6 2017
\(a,\)\(x\)\(=\frac{3}{6}-\frac{8}{16}=\frac{1}{2}-\frac{1}{2}=0\)
\(b,\)\(\frac{12}{16}\)\(:\)\(x\)\(=\frac{32}{64}\)
\(=>\) \(x\)\(=\)\(\frac{12}{16}:\frac{32}{64}\)
\(x\) \(=\)\(\frac{12}{16}.\frac{64}{32}\)
\(x\)\(=\)\(\frac{3}{4}.2\)
\(x\)\(=\)\(\frac{6}{4}=\frac{3}{2}\)
T
4
25 tháng 9 2018
Câu 1:
x=0
Câu 2:
x=4
Câu 3:
x=1
Câu 4:
x=3
k mik nha
MV
23 tháng 4 2017
9) \(\dfrac{x}{4}=\dfrac{9}{x}\)
Theo định nghĩa về hai phân số bằng nhau, ta có:
\(4\cdot9=x^2\\ 36=x^2\Rightarrow\left[{}\begin{matrix}x=6\\x=-6\end{matrix}\right.\)
8)
\(x:\dfrac{5}{3}+\dfrac{1}{3}=-\dfrac{2}{5}\\ x:\dfrac{5}{3}=-\dfrac{2}{5}+\dfrac{1}{3}\\ x:\dfrac{5}{3}=-\dfrac{1}{15}\\ x=\dfrac{1}{15}\cdot\dfrac{5}{3}\\ x=\dfrac{1}{9}\)
7)
\(2x-16=40+x\\ 2x-x=40+16\\ x\left(2-1\right)=56\\ x=56\)
6)
\(1\dfrac{1}{2}+x=\dfrac{3}{2}-7\\ \dfrac{3}{2}+x=\dfrac{3}{2}-7\\ \dfrac{3}{2}-\dfrac{3}{2}=-7-x\\ -7-x=0\\ x=-7-0\\ x=-7\)
5)
\(3\dfrac{1}{2}-\dfrac{1}{2}x=\dfrac{2}{3}\\ \dfrac{7}{2}-\dfrac{1}{2}x=\dfrac{2}{3}\\ \dfrac{1}{2}x=\dfrac{7}{2}-\dfrac{2}{3}\\ \dfrac{1}{2}x=\dfrac{17}{6}\\ x=\dfrac{17}{6}:\dfrac{1}{2}\\ x=\dfrac{17}{3}\)
4)
\(x\cdot\left(x+1\right)=0\Rightarrow\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
3)
\(\left(\dfrac{2x}{5}+2\right):\left(-4\right)=-1\dfrac{1}{2}\\ \left(\dfrac{2x}{5}+2\right):\left(-4\right)=-\dfrac{3}{2}\\ \dfrac{2x}{5}+2=-\dfrac{3}{2}\cdot\left(-4\right)\\ \dfrac{2x}{5}+2=6\\ \dfrac{2x}{5}=6-2\\ \dfrac{2x}{5}=4\\ 2x=4\cdot5\\ 2x=20\\ x=20:2\\ x=10\)
2)
\(\dfrac{1}{3}+\dfrac{1}{2}:x=-0,25\\ \dfrac{1}{3}+\dfrac{1}{2}:x=-\dfrac{1}{4}\\ \dfrac{1}{2}:x=-\dfrac{1}{4}-\dfrac{1}{3}\\ \dfrac{1}{2}:x=-\dfrac{7}{12}\\ x=\dfrac{1}{2}:-\dfrac{7}{12}\\ x=-\dfrac{6}{7}\)
1)
\(\dfrac{4}{3}+x=\dfrac{2}{15}\\ x=\dfrac{2}{15}-\dfrac{4}{3}x=-\dfrac{6}{5}\)
31 tháng 1 2022
a: \(\Leftrightarrow x^3=\dfrac{539}{64}\)
hay \(x=\dfrac{7\sqrt{11}}{4}\)
c: \(\Leftrightarrow2^{2x-1}=2^9\cdot2^2=2^{11}\)
=>2x-1=11
hay x=6
d: \(\Leftrightarrow x^{17}-x=0\)
\(\Leftrightarrow x\left(x-1\right)\left(x+1\right)=0\)
hay \(x\in\left\{0;1;-1\right\}\)
3^2=9
4^3=64
2^4=16
\(3^x=9\Rightarrow x=2\)
\(4^x=64\Rightarrow x=3\)
\(2^x=16\Rightarrow x=4\)
Chúc bn hok tốt!