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12.(x-3):3=64+8
12.(x-3):3=72
12.(x-3) =72.3
12.(x-3) =216
x-3 =216:12
x-3 =18
x =18+3
x =21
100-7.(x-5)=65
7.(x-5)=100-65
7.(x-5)=35
x-5=35:7
x-5=5
x =5+5
x =10
Vậy x = 10
a) (2x)5 : 43 = 815 => 25x = 815.43 = (23)15.(22)3 = 245.26 = 251 => 5x = 51 => x = 10,2
b) (32)x .93 = 2439 => 32x = 2439 : 93 = (35)9 : (32)3 = 345 : 36 = 339 => 2x = 39 => x = 19,5
c) (1/125)3.5x = 255 => 5x = 255 : (1/125)3 = (52)5 : (1/53)3 = 510 : (5-3)3 = 510 : 5-9 = 519 => x = 19
d) 1/81 : 3x = 1/729 => 3x = 1/81 : 1/729 = 1/34.729 = 3-4.36 = 32 => x = 2
e) (5x - 2)4 = 168 = (162)4 = 2564
=> 5x - 2 = -256 ; 256 => 5x = -254 ; 258 => x = -50,8 ; 51,6
P/S : Thay x = 10,2 vào câu a , x = 19,5 vào câu b sẽ thấy điều hư cấu : 210,2 và 919,5.Ko thể tính được giá trị của 2 lũy thừa này.
\(5x-2.\left(x-1\right)=4.3.125.\left(-25\right).8\)
\(5x-2x+2=-300000\)
\(3x+2=-300000\)
\(3x=-300000-2\)
\(3x=-300002\)
\(x=-\frac{300002}{3}\)
c) \(5x-7=3x+9\)
d) \(5x-\left|9-7x\right|=3\)
e) \(-5+\left|3x-1\right|+6=\left|-4\right|\)
h) \(5^{-1}.25^x=125\)
\(\Rightarrow\frac{1}{5}.25^x=125\)
\(\Rightarrow25^x=125:\frac{1}{5}\)
\(\Rightarrow25^x=625\)
\(\Rightarrow25^x=25^2\)
\(\Rightarrow x=2\)
Vậy \(x=2.\)
Chúc bạn học tốt!
g) \(\left(x-1\right)^2=\left(x-1\right)^4\)
\(\Rightarrow\left(x-1\right)^2-\left(x-1\right)^4=0\)
\(\Rightarrow\left(x-1\right)^2.\left[1-\left(x-1\right)^2\right]=0\)
\(\Rightarrow\left[{}\begin{matrix}\left(x-1\right)^2=0\\1-\left(x-1\right)^2=0\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x-1=0\\\left(x-1\right)^2=1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=0+1\\x-1=1\\x-1=-1\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=1\\x=1+1\\x=\left(-1\right)+1\end{matrix}\right.\Rightarrow\left[{}\begin{matrix}x=1\\x=2\\x=0\end{matrix}\right.\)
Vậy \(x\in\left\{1;2;0\right\}.\)
i) \(\left|x+1\right|+\left|x+2\right|+\left|x+3\right|=4x\)
Ta có:
\(\left\{{}\begin{matrix}\left|x+1\right|\ge0\\\left|x+2\right|\ge0\\\left|x+3\right|\ge0\end{matrix}\right.\forall x.\)
\(\Rightarrow\left|x+1\right|+\left|x+2\right|+\left|x+3\right|\ge0\) \(\forall x.\)
\(\Rightarrow4x\ge0\)
\(\Rightarrow x\ge0.\)
Lúc này ta có: \(\left(x+1\right)+\left(x+2\right)+\left(x+3\right)=4x\)
\(\Rightarrow x+1+x+2+x+3=4x\)
\(\Rightarrow\left(x+x+x\right)+\left(1+2+3\right)=4x\)
\(\Rightarrow3x+6=4x\)
\(\Rightarrow6=4x-3x\)
\(\Rightarrow6=1x\)
\(\Rightarrow x=6\left(TM\right).\)
Vậy \(x=6.\)
Chúc bạn học tốt!
a, \(\left(3x-7\right)-\left(-5-7x\right)=4x+9\)
\(\Leftrightarrow3x-7+5+7x=4x+9\)
\(\Leftrightarrow3x+7x-4x=9+7-5\)
\(\Leftrightarrow\left(3+7-6\right)x=11\Rightarrow4x=11\Rightarrow x=\frac{11}{4}\notin Z\)
Vậy : \(x\in\varnothing\)
b, \(\left(3x-7\right)-\left(-5-7x\right)=5x+8\)
\(\Leftrightarrow3x-7+5+7x=5x+8\)
\(\Leftrightarrow3x+7x-5x=8+7-5\)
\(\Leftrightarrow\left(3+7-5\right)x=10\Rightarrow5x=10\Rightarrow x=10\div5=2\in Z\)
Vậy : x = 2
c, \(\left(3x-2\right)^3=125\Leftrightarrow\left(3x-2\right)^3=5^3\)
\(\Rightarrow3x-2=5\Rightarrow3x=5+2\Rightarrow3x=7\)
\(\Rightarrow x=7\div3\Rightarrow x=\frac{7}{3}\notin Z\)
Vậy \(x\in\varnothing\)
a, (3x-7)-(-5-7x)=4x+9
3x-7+5+7x=4x+9
3x+7x-4x=9+7-5
6x=11
x=11/6(thuộc Z t/m)
Vậy...
b, (3x-7)-(-5-7x)=5x+8
3x-7+5+7x=5x+8
3x+7x-5x=8+7-5
5x=10
x=2(thuộc Z t/m)
vây...
c, (3x-2)^3=125
(3x-2)^3=5^3
3x-2=5
x=7/3(thuộc Z thỏa mãn)
Vậy...
\(\left(5x-\frac{1}{5}\right)^3=\frac{8}{125}\)
\(\left(5x-\frac{1}{5}\right)^3=\left(\frac{2}{5}\right)^3\)
\(5x-\frac{1}{5}=\frac{2}{5}\)
\(5x=\frac{3}{5}\)
\(x=\frac{3}{5}:5\)
\(x=\frac{3}{25}\)