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a) \(\frac{3}{7}-\frac{1}{7}x=\frac{2}{3}\)
=> \(\frac{1}{7}x=\frac{3}{7}-\frac{2}{3}=-\frac{5}{21}\)
=> \(x=-\frac{5}{21}:\frac{1}{7}=-\frac{5}{21}\cdot7=-\frac{5}{3}\)
b) \(3x^2-2=72\)=> 3x2 = 74 => x2 = 74/3 => x không thỏa mãn
c) \(\left(19x+2\cdot5^2\right):14=\left(13-8\right)^2-4^2\)
=> \(\left(19x+2\cdot25\right):14=5^2-4^2=9\)
=> \(\left(19x+50\right):14=9\)
=> \(19x+50=126\)
=> \(19x=76\)
=> x = 4
d) \(x:\frac{1}{2}+x:\frac{1}{4}+x:\frac{1}{8}+x:\frac{1}{16}+x:\frac{1}{32}=343\)
=> \(x\cdot2+x\cdot4+x\cdot8+x\cdot16+x\cdot32=343\)
=> \(x\left(2+4+8+16+32\right)=343\)
=> x . 62 = 343
=> x = 343/62
a)x+15=-7
x=(-7)-15
x=-22
b)\(\left(5x-2\right).8^3=8^4\)
(5x-2).512=4096
(5x-2)=4096:512
(5x-2)=8
5x=8+2
5x=10
x=10:5
x=2
c)|x-1|=2
=>x-1=2 hoac x-1=-2
x=2+1 x=-2+1
x=3 x=-1
a/ => x = (-7) - 15 = -22
Vậy x = -22
b/ (5x - 2) . 83 = 84
=> 5x - 2 = 8
=> 5x = 10
=> x = 2
Vậy x = 2
c/ => x - 1 = 2 => x = 3
hoặc x - 1 = -2 => x = -1
Vậy x = 3 ; x = -1
a: \(3^x-2=2^7\)
\(\Leftrightarrow3^x=128+2=130\)(vô lý)
b: \(4^{x+1}=64\)
=>x+1=3
hay x=2
c: \(\left(5x+1\right)^2=1^{2016}=1\)
=>5x+1=1 hoặc 5x+1=-1
=>x=0 hoặc x=-2/5
d: \(2^{2\left(x-1\right)}=8\)
=>2(x-1)=3
=>x-1=3/2
hay x=5/2
a) x=3
b) x=1
c) x=1 hoặc -5
d) x=2
e) x=2
g) x=2
h) x=1 hoặc x=0 hoặc x=-1
i) x=-1 hoặc x=0
\(a.4^x=64\)
\(4^x=4^3\)
\(\Rightarrow x=3\)
\(b,3^{x\times4}=81\)
\(3^{x\times4}=3^4\)
\(x\times4=4\)
\(\Rightarrow x=1\)
\(c,\left(2+x\right)^4=81\)
\(\left(2+x\right)^4=3^4\)
\(2+x=3\)
\(x=3-2\)
\(x=1\)
\(d,5^{x\times5}=125\)
\(5^{x\times5}=5^3\)
\(x\times5=3\)
\(x=3:5\)
\(x=\frac{3}{5}\)
\(\frac{-4}{8}=\frac{x}{-10}=\frac{-7}{y}\)
Vậy x = -4 . -10 : 8 = 5
=> Y = -10 . 7 : 5 = 14
Câu 2 ( CHỊU) BÓ TAY
\(A=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+...+\frac{1}{10^2}\)
\(\Rightarrow A< \frac{1}{2}+\frac{1}{3}+\frac{1}{4}+...+\frac{1}{10}\)
\(\Rightarrow A< \frac{1}{10}+\frac{1}{10}+\frac{1}{10}+...+\frac{1}{10}\) ( 9 số hạng \(\frac{1}{10}\))
\(\Rightarrow A< \frac{9}{10}< 1\)
Vậy \(A< 1\left(đpcm\right)\)
a; 3.(\(\dfrac{1}{2}\)\(x\) - 1) = - \(\dfrac{3}{4}\)
\(\dfrac{1}{2}x-1\) = - \(\dfrac{3}{4}\) : 3
\(\dfrac{1}{2}x\) - 1 = - \(\dfrac{1}{4}\)
\(\dfrac{1}{2}x\) = - \(\dfrac{1}{4}+1\)
\(\dfrac{1}{2}x\) = \(\dfrac{3}{4}\)
\(x\) = \(\dfrac{3}{4}\) : \(\dfrac{1}{2}\)
\(x\) = \(\dfrac{3}{2}\)
Vậy \(x\) = \(\dfrac{3}{2}\)
b; (\(\dfrac{1}{2}\))\(x\) = \(\dfrac{1}{8}\)
(\(\dfrac{1}{2}\))\(x\) = (\(\dfrac{1}{2}\))3
\(x\) = 3
Vậy \(x\) = 3