(2/3)^ x+2 + (2/3)^ x+1=20/27
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21 tháng 2 2021
1: Ta có: 7x+6(3-x)=27-20+73
\(\Leftrightarrow7x+18-6x=80\)
\(\Leftrightarrow x=80-18=62\)
Vậy: x=62
2: Ta có: \(6x-5\left(x-7\right)=\left(27-514\right)-486-73\)
\(\Leftrightarrow6x-5x+35=27-514-486-73\)
\(\Leftrightarrow x+35=-1046\)
\(\Leftrightarrow x=-1081\)
Vậy: x=-1081
VH
0
VH
1
30 tháng 1 2021
1: Tìm x
a) Ta có: \(2\cdot3^x=3^{12}\cdot34+20\cdot27^4\)
\(\Leftrightarrow2\cdot3^x=3^{12}\cdot34+20\cdot3^{12}\)
\(\Leftrightarrow2\cdot3^x=3^{12}\cdot\left(34+20\right)\)
\(\Leftrightarrow2\cdot3^x-3^{12}\cdot54=0\)
\(\Leftrightarrow2\cdot3^x=3^{12}\cdot2\cdot27\)
\(\Leftrightarrow3^x=3^{12}\cdot3^3\)
\(\Leftrightarrow3^x=3^{15}\)
hay x=15
Vậy: x=15
b) Ta có: \(\left(2^x+1\right)^2+3\left(2^2+1\right)=2^2\cdot10\)
\(\Leftrightarrow\left(2^x+1\right)^2=40-3\cdot5=25\)
\(\Leftrightarrow\left[{}\begin{matrix}2^x+1=5\\2^x+1=-5\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}2^x=4\\2^x=-6\left(loại\right)\end{matrix}\right.\Leftrightarrow x=2\)
Vậy: x=2
PT
1
CM
6 tháng 6 2018
a. x × 3 = 27
x = 27 : 3
x = 9
b. 4 × x = 20
x = 20 : 4
x = 5
c. 10 + x : 2 = 20
x : 2 = 20 – 10
x : 2 = 10
x = 10 × 2
x = 20
d. x × 3 = 27 + 3
x × 3 = 30
x = 30 : 3
x = 10
e. 27 : x = 789 – 780
27 : x = 9
x = 27 : 9
x = 3
CQ
1
30 tháng 7 2018
\(\left(\frac{2}{3}\right)^{x+2}+\left(\frac{2}{3}\right)^{x+1}=\frac{20}{27}\)
\(\left(\frac{2}{3}\right)^x+\left(\frac{2}{3}\right)^2+\left(\frac{2}{3}\right)^x+\left(\frac{2}{3}\right)^1=\frac{20}{27}\)
\(\left(\frac{2}{3}\right)^{2x}+\frac{4}{9}+\frac{2}{3}=\frac{20}{27}\)
\(\left(\frac{2}{3}\right)^{2x}+\frac{10}{9}=\frac{20}{27}\)
\(\left(\frac{2}{3}\right)^{2x}=\frac{20}{27}-\frac{10}{9}\)
\(\left(\frac{2}{3}\right)^{2x}=\frac{110}{63}\)
MÌnh chịu
PL
30 tháng 7 2018
Ta có : \(\left(\frac{2}{3}\right)^{x+2}+\left(\frac{2}{3}\right)^{x+1}=\frac{20}{27}\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{x+1}\left(\frac{2}{3}+1\right)=\frac{20}{27}\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{x+1}\frac{5}{3}=\frac{20}{27}\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{x+1}=\frac{20}{27}.\frac{3}{5}\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{x+1}=\frac{9}{4}\)
\(\Leftrightarrow\left(\frac{2}{3}\right)^{x+1}=\left(\frac{2}{3}\right)^2\)
=> x + 1 = 2
=> x = 1
6 tháng 4 2023
a: =>x/27+1=-2/3
=>x/27=-5/3
=>x=-45
b: \(\Leftrightarrow x-4=\dfrac{2}{5}:\dfrac{20}{21}=\dfrac{2}{5}\cdot\dfrac{21}{20}=\dfrac{42}{100}=\dfrac{21}{50}\)
=>x=221/50
c: \(\Leftrightarrow x+\dfrac{2}{3}=\dfrac{4}{60}=\dfrac{1}{15}\)
=>x=1/15-2/3=1/15-10/15=-9/15=-3/5
d: \(\Leftrightarrow x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{15}{14}\cdot\dfrac{21}{20}\)
=>\(x\cdot\dfrac{3}{5}=\dfrac{1}{5}-\dfrac{3}{2}\cdot\dfrac{3}{4}=\dfrac{1}{5}-\dfrac{9}{8}=\dfrac{-37}{40}\)
=>x=-37/24
e: =>-3/7x=84/45
=>x=-196/45
f: =>11/10x=-2/3
=>x=-20/33
P
0
\(\left(\dfrac{2}{3}\right)^{x+2}+\left(\dfrac{2}{3}\right)^{x+1}=\dfrac{20}{27}\\ \left(\dfrac{2}{3}\right)^{x+1}\cdot\left(\dfrac{2}{3}+1\right)=\dfrac{20}{27}\\ \left(\dfrac{2}{3}\right)^{x+1}\cdot\dfrac{5}{3}=\dfrac{20}{27}\\ \left(\dfrac{2}{3}\right)^{x+1}=\dfrac{20}{27}:\dfrac{5}{3}=\dfrac{4}{9}\\ \left(\dfrac{2}{3}\right)^{x+1}=\left(\dfrac{2}{3}\right)^2\\ x+1=2\\ x=2-1\\ x=1\)