\(\left(0,4x-1,3\right)^2=5,29\)

\(\left(0,4x-1,3\right)^2=\left(\pm2,3\right)^2\)

+) 0,4x - 1,3 = 2,3

0,4x = 3,6

x = 9

+) 0,4x - 1,3 = -2,3

0,4x = -1

x = -2,5

Vậy,........

(0,4x - 1,3)² = 5,29

(0,4x - 1,3)² = 2,3²

=> \(\orbr{\begin{cases}0,4x-1,3=2,3\\0,4x-1,3=-2,3\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}0,4x=3,6\\0,4x=-1\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=9\\x=-\frac{5}{2}\end{cases}}\)

\(\left(0,4x-1,3\right)^2=5,29\)

Ta xét 2th:

Th1: \(0,4x-1,3=\sqrt{5,29}\)

\(0,4x-1,3=\sqrt{5,29}+1,3\)

=> x = 9

Th2: \(0,4x-1,3=-\sqrt{5,29}\)

\(0,4x-1,3=-\sqrt{5,29}+1,3\)

=> x = -2,5

\(\Rightarrow\orbr{\begin{cases}x=9\\x=-2,5\end{cases}}\)

\(a,\left(\dfrac{3}{5}-\dfrac{2}{3}x\right)^3=-\dfrac{64}{125}\)

\(\left(\dfrac{3}{5}-\dfrac{2}{3}x\right)^3=\left(\dfrac{-4}{5}\right)^3\)

\(\dfrac{3}{5}-\dfrac{2}{3}x=-\dfrac{4}{5}\)

\(-\dfrac{2}{3}x=-\dfrac{4}{5}-\dfrac{3}{5}\)

\(-\dfrac{2}{3}x=-\dfrac{7}{5}\)

\(x=\dfrac{21}{10}\)

\(b,\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{2}{3}\right)^6\)

\(\left(x-\dfrac{2}{9}\right)^3=\left(\dfrac{4}{9}\right)^3\)

\(x-\dfrac{2}{9}=\dfrac{4}{9}\)

\(x=\dfrac{2}{3}\)

\(c,\left(0,4x-1,3\right)^2=5,29\)

\(\left(0,4x-1,3\right)^2=2,3^2=\left(-2,3\right)^2\)

TH1: \(0,4x-1,3=2,3\)

\(0,4x=3,6\)

\(x=9\)

TH2: \(0,4x-1,3=-2,3\)

\(0,4x=-1\)

\(x=-\dfrac{5}{2}\)

=.= hok tốt!!

Bài 10:
a)  (1/3)ⁿ = 1/81
=> (1/3)ⁿ = (1/3)⁴
=>     n   =    4

b)  -512/343 = (-8/7)ⁿ
=> (-8/7)³    = (-8/7)ⁿ
=>     3       =     n     (hay n = 3)

c)  (-3/4)ⁿ = 81/256
=> (-3/4)ⁿ = (-3/4)⁴
=>     n    =     4

d)  64/(-2)ⁿ = (-2)³
=> 64/(-2)ⁿ = -8
=>     (-2)ⁿ = -8
=>     (-2)ⁿ = (-2)³
=>        n  =   3

Bài 11: (không có y để tìm nhé)
a)  (0,4x - 1,3)² = 5,29
=> (0,4x - 1,3)² = (2,3)²
=>  0,4x - 1,3    =  2,3
=>  0,4x           = 3,6
=>       x           = 9

b)  (3/5 - 2/3x)³ = -64/125
=> (3/5 - 2/3x)³ = (-4/5)³
=>  3/5 - 2/3x   =  -4/5
=>          2/3x   = 7/5
=>              x    = 21/10

a: \(\Leftrightarrow3^x\cdot\left(\dfrac{2}{3}\cdot3-7\right)=405\)

\(\Leftrightarrow3^x=-81\)(vô lý)

b: \(\left(0,4x-1,3\right)^2=5,29\)

=>0,4x-1,3=2,3 hoặc 0,4x-1,3=-2,3

=>0,4x=3,6 hoặc 0,4x=-1

=>x=9 hoặc x=-2,5

c: \(5\cdot2^{x+1}\cdot2^{-2}-2^x=284\)

\(\Leftrightarrow2^x\cdot5\cdot2\cdot2^{-2}-2^x=284\)

\(\Leftrightarrow2^x\cdot\left(\dfrac{5}{2}-1\right)=284\)

\(\Leftrightarrow2^x=\dfrac{568}{3}\)(vô lý)

d: \(\Leftrightarrow4^x\left(1+4^3\right)=4160\)

\(\Leftrightarrow4^x=64\)

hay x=3

a/ \(\frac{2}{3}.3^{x+1}-7.3^x=405\)

<=> 2.3^x-7.3^x=-405

<=> 5.3^x=405

<=> 3^x=81 = 3⁴

=> x=4

b/ (0,4x-1,3)²=5,29=(2,3)²

=> \(\hept{\begin{cases}0,4x-1,3=2,3\\0,4x-1,3=-2,3\end{cases}}\)=> \(\hept{\begin{cases}x=9\\x=-\frac{5}{2}\end{cases}}\)

c/ 5.2^x+1.2^-2-2^x=384

<=> 5.2^x-1-2.2^x-1=384

<=> 3.2^x-1=384

<=> 2^x-1=128=2⁷

=> x-1=7 => x=8

d/ 3^x+2.5^y=45^x

<=> 3^x+2.5^y=3^2x.5^x

=> \(\hept{\begin{cases}x+2=2x\\x=y\end{cases}}\)=> x=y=2

a, đề sai

b) \(\left(x-3\right)^{10}=\left(x-3\right)^{30}\)

\(\Rightarrow\left\{{}\begin{matrix}x-3=-1\\x-3=0\\x-3=1\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=2\\x=3\\x=4\end{matrix}\right.\)

Vậy .....

c) \(\left(x+1,5\right)^8+\left(2,7-y\right)^{12}=0\)

Vì: \(\left\{{}\begin{matrix}\left(x+1,5\right)^8\ge0\forall x\\\left(2,7-y\right)^{12}\ge0\forall y\end{matrix}\right.\)

\(\Rightarrow\) để bt = 0

=>\(\left\{{}\begin{matrix}\left(x+1,5\right)^8=0\\\left(2,7-y\right)^{12}=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x+1,5=0\\2,7-y=0\end{matrix}\right.\)

=> \(\left\{{}\begin{matrix}x=-1,5\\y=2,7\end{matrix}\right.\)

Vậy.............

\(x:60\%+0,4x=2\)
\(\Rightarrow\dfrac{5}{3}x+0,4x=2\)
\(\Rightarrow\left(\dfrac{5}{3}+0,4\right)x=2\)
\(\Rightarrow\dfrac{31}{15}x=2\)
\(\Rightarrow x=2:\dfrac{31}{15}\)
\(\Rightarrow x=\dfrac{30}{31}\)
#DarkPegasus

60% + 0,4x=2

0,4x=2-60%

0,4x=2-0,6

0,4x=1,4

x=1,4:0,4

x=3,5

           Vậy:...

 nhớ ticks nhe

\(\dfrac{60}{100}+0,4x=2\)

\(\dfrac{3}{5}+0,4x=2\)

\(0,4x=2-\dfrac{3}{5}\)

\(0,4x=\dfrac{7}{5}\)

\(x=\dfrac{7}{5}:0,4\)

\(x=3,5\)