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VT
5
23 tháng 9 2018
2x + 2x + 2 = 160
2x + 2x. 4 = 160
2x(1 + 4) = 160
2x.5 = 160
2x = 160 : 5
2x = 32
2x = 25
=> x = 5
23 tháng 9 2018
\(2^x+2^{x+2}=160\)
\(2^x+2^x.4=160\)
\(2^x.5=160\)
\(2^x=32=>x=5\)
DN
0
NT
1
13 tháng 10 2023
\(\dfrac{1}{10}+\dfrac{1}{40}+\dfrac{1}{88}+...+\dfrac{1}{\left(x+2\right)\left(x+5\right)}=\dfrac{3}{20}\)
\(\Rightarrow\dfrac{1}{2\cdot5}+\dfrac{1}{5\cdot8}+\dfrac{1}{8\cdot11}+...+\dfrac{1}{\left(x+2\right)\left(x+5\right)}=\dfrac{3}{20}\)
\(\Rightarrow\dfrac{1}{3}\cdot\left(\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+...+\dfrac{3}{\left(x+2\right)\left(x+5\right)}\right)=\dfrac{3}{20}\)
\(\Rightarrow\dfrac{3}{2\cdot5}+\dfrac{3}{5\cdot8}+..+\dfrac{3}{\left(x+2\right)\left(x+5\right)}=\dfrac{9}{20}\)
\(\Rightarrow\dfrac{1}{2}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{8}+...+\dfrac{1}{x+2}-\dfrac{1}{x+5}=\dfrac{9}{20}\)
\(\Rightarrow\dfrac{1}{2}-\dfrac{1}{x+5}=\dfrac{9}{20}\)
\(\Rightarrow\dfrac{1}{x+5}=\dfrac{1}{2}-\dfrac{9}{20}\)
\(\Rightarrow\dfrac{1}{x+5}=\dfrac{1}{20}\)
\(\Rightarrow x+5=20\)
\(\Rightarrow x=20-5\)
\(\Rightarrow x=15\)
NT
0
5 tháng 12 2017
Câu 1 : \(\frac{x+2}{18}+\frac{x+2}{19}+\frac{x+2}{20}=\frac{x+2}{21}+\frac{x+2}{22}\)
=> \(\frac{x+2}{18}+\frac{x+2}{19}+\frac{x+2}{20}-\frac{x+2}{21}-\frac{x+2}{22}=0\)
=> x+2 . ( \(\frac{1}{18}+\frac{1}{19}+\frac{1}{20}-\frac{1}{21}-\frac{1}{22}\)) = 0
Vì \(\frac{1}{18}+\frac{1}{19}_{ }+\frac{1}{20}-\frac{1}{21}-\frac{1}{22}\ne0\)nên x+2=0
=> x= 0 - 2 = -2
Vậy x = -2
TM
0
NQ
0
2x + 1 - 3.2x - 2 = 40
<=> 2x - 2 + 3 - 3.2x - 2 = 40
<=> 8.2x - 2 - 3.2x - 2 = 40
<=> 5.2x - 2 = 40
<=> 2x - 2 = 8
<=> 2x - 2 = 23
<=> x - 2 = 3
<=> x = 5
Trả lời:
2x + 1 - 3.2x - 2 = 40
<=> 2x . 2 - 3 . 2x : 22 = 40
<=> 2x . 2 - 3 . 2x : 4 = 40
<=> 2x . 2 - 3 . 2x . 1/4 = 40
<=> 2x .( 2 - 3 . 1/4 ) = 40
<=> 2x . 1,25 = 40
<=> 2x = 32
<=> 2x = 25
=> x = 5