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1.
a) a=5 vì 52 = 25
b) a=3 vì 33 = 27
2.
a)x=2 vì 52 = 25
b ) x= 4 vì 43 = 64
c ) x=1 vì 21 . 2 =4
chúc bn hok giỏi

a: \(2^{x}\cdot4=128\)
=>\(2^{x}=\frac{128}{4}=32=2^5\)
=>x=5
b: \(x^{15}=x\)
=>\(x^{15}-x=0\)
=>\(x\left(x^{14}-1\right)=0\)
=>\(\left[\begin{array}{l}x=0\\ x^{14}-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x^{14}=1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=1\end{array}\right.\)
c: \(\left(2x+1\right)^3=125\)
=>\(\left(2x+1\right)^3=5^3\)
=>2x+1=5
=>2x=5-1=4
=>\(x=\frac42=2\)
d: \(\left(x-5\right)^4=\left(x-5\right)^6\)
=>\(\left(x-5\right)^6-\left(x-5\right)^4=0\)
=>\(\left(x-5\right)^4\cdot\left\lbrack\left(x-5\right)^2-1\right\rbrack=0\)
=>\(\left(x-5\right)^4\cdot\left(x-5-1\right)\left(x-5+1\right)=0\)
=>\(\left(x-5\right)^4\cdot\left(x-6\right)\left(x-4\right)=0\)
=>\(\left[\begin{array}{l}x-5=0\\ x-6=0\\ x-4=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=5\\ x=6\\ x=4\end{array}\right.\)

a) 25 + 3x = 25 - 1
3x = -1
x = -1/3
b) (6x-39):13 = 201
6x-39 = 2613
6x = 2652
x = 442
c) 2x + 35:34 = 510 : 58
2x + 3 = 25
2x = 22
...

a: \(\Leftrightarrow\dfrac{8}{5}+\dfrac{2}{5}\cdot x=\dfrac{16}{5}\)
=>2/5x=8/5
=>x=4
b: \(\Leftrightarrow\left(\dfrac{1}{24}-\dfrac{1}{25}+\dfrac{1}{25}-\dfrac{1}{26}+...+\dfrac{1}{39}-\dfrac{1}{40}\right)\cdot120+\dfrac{1}{3}x=-4\)
\(\Leftrightarrow x\cdot\dfrac{1}{3}+2=-4\)
=>1/3x=-6
=>x=-18
c: =>2|x-1/3|=0,24-4/5=-0,56<0

a) x- 25%x= 1/2<=>x-1/4x=1/2<=>3/4x=1/2<=>x=1/2:3/4=2/3
b)\(\left(50\%x+2\frac{1}{4}\right).\frac{-2}{3}=\frac{17}{6}\Leftrightarrow-\frac{1}{3}x-\frac{3}{2}=\frac{17}{6}\Leftrightarrow x=-13\)
c)\(\left(3\frac{x}{7}+1\right):\left(-4\right)=\frac{-1}{28}\Leftrightarrow\frac{28+x}{7}:\left(-4\right)=\frac{-1}{28}\Leftrightarrow\frac{28+x}{-28}=\frac{1}{-28}\Leftrightarrow28+x=1\Leftrightarrow x=-27\)
d)\(\left(1\frac{1}{3}-25\%-\frac{5}{12}\right)-2x=1,6:\frac{3}{5}\Leftrightarrow\frac{2}{3}-2x=\frac{8}{3}\Leftrightarrow x=-1\)
a)x-25%x=1/2
x-1/4x=1/2
x.(1-1/4)=1/2
x.3/4=1/2
x=1/2:3/4
x=2/3

mk sắp phải đi học rồi các bạn giúp mình với có đc ko mk nhớ sẽ đền đáp công ơn của bạn

Bài 1:
a) \(-\frac{4}{5}-\frac{8}{25}\left(\frac{-5}{2}-0,125\right)\\ =-\frac{4}{5}-\frac{8}{25}\left(\frac{-5}{2}-\frac{1}{8}\right)\\ =-\frac{4}{5}-\frac{8}{25}\left(\frac{-20}{8}-\frac{1}{8}\right)\\ =-\frac{4}{5}-\frac{8}{25}\cdot\frac{-21}{8}\\ =-\frac{4}{5}-\frac{-21}{25}\\ =\frac{-4}{5}+\frac{21}{25}\\ =\frac{-20}{25}+\frac{21}{25}=\frac{1}{25}\)
c) \(5\frac{1}{2}-4\frac{2}{3}:\frac{16}{9}-3\frac{1}{3}:\frac{16}{9}\\ =5\frac{1}{2}-\left(4\frac{2}{3}:\frac{16}{9}+3\frac{1}{3}:\frac{16}{9}\right)\\ =5\frac{1}{2}-\left(4\frac{2}{3}+3\frac{1}{3}\right):\frac{16}{9}\\ =5\frac{1}{2}-8\cdot\frac{9}{16}\\ =\frac{11}{2}-\frac{9}{2}=\frac{2}{2}=1\)
Bài 2:
a) \(\left(20\%x+\frac{2}{5}x-2\right):\frac{1}{3}=-2013\\ \left(\frac{1}{5}x+\frac{2}{5}x-2\right)\cdot3=-2013\\ \left[x\left(\frac{1}{5}+\frac{2}{5}\right)-2\right]=\left(-2013\right):3\\ x\cdot\frac{3}{5}-2=-671\\ x\cdot\frac{3}{5}=-671+2\\ x\cdot\frac{3}{5}=-669\\ x=\left(-669\right):\frac{3}{5}\\ x=\left(-669\right)\cdot\frac{5}{3}\\ x=-1115\)Vậy x = -1115
b) \(\left(4,5-2\left|x\right|\right)\cdot1\frac{4}{7}=\frac{11}{14}\\ \left(\frac{9}{2}-2\left|x\right|\right)\cdot\frac{11}{7}=\frac{11}{14}\\ \frac{9}{2}-2\left|x\right|=\frac{11}{14}:\frac{11}{7}\\ \frac{9}{2}-2\left|x\right|=\frac{11}{14}\cdot\frac{7}{11}\\ \frac{9}{2}-2\left|x\right|=\frac{1}{2}\\ 2\left|x\right|=\frac{9}{2}-\frac{1}{2}\\ 2\left|x\right|=4\\ \left|x\right|=4:2\\ \left|x\right|=2\\ \Rightarrow\left[{}\begin{matrix}x=2\\x=-2\end{matrix}\right.\)Vậy x ∈ {2 ; -2}
a) Ta có : 5 x : 5 2 = 5 2 nên x = 4,
b) Ta có: 5 x + 1 : 5 = 5 4 nên x = 4.
c) Ta có : 4 2 x - 1 : 4 = 4 2 nên x = 2.