Mk sửa đề nha :

\(C=\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}+\frac{12}{7}\)

   \(=\frac{-5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{12}{7}\)

   \(=\frac{-5}{7}.1+\frac{12}{7}\)

   \(=\frac{-5}{7}+\frac{12}{7}\)

   \(=1\)

Study well ! >_<

1 ) <=> 5.3^x = 405

<=> 3^x = 81 = 3⁴

=> x = 4

2 ) <=> 2^x ( 7.2³ - 5.2² + 1 ) = 1184

<=> 2^x ( 7.8 - 5.4 + 1 ) = 1184

<=> 2^x ( 56 - 20 + 1 ) = 1184

<=> 2^x . 37 = 1184

<=> 2^x = 32 = 2⁵

=> x = 5

1 ) <=> 5.3^x = 405

<=> 3^x = 81 = 3⁴

=> x = 4

2 ) <=> 2^x ( 7.2³ - 5.2² + 1 ) = 1184

<=> 2^x ( 7.8 - 5.4 + 1 ) = 1184

<=> 2^x ( 56 - 20 + 1 ) = 1184

<=> 2^x . 37 = 1184

<=> 2^x = 32 = 2⁵

=> x = 5

 mk để mk đc trong 290đ đc ko!? 

1: =>3^x=81

=>x=4

2: =>2^x=8

=>x=3

3: =>x^3=2^3

=>x=2

4: =>x^20-x=0

=>x(x^19-1)=0

=>x=0 hoặc x=1

5: =>2^x=32

=>x=5

6: =>(2x+1)^3=9^3

=>2x+1=9

=>2x=8

=>x=4

7: =>x^3=115

=>\(x=\sqrt[3]{115}\)

8: =>(2x-15)^5-(2x-15)^3=0

=>(2x-15)^3*[(2x-15)^2-1]=0

=>2x-15=0 hoặc (2x-15)^2-1=0

=>2x-15=0 hoặc 2x-15=1 hoặc 2x-15=-1

=>x=15/2 hoặc x=8 hoặc x=7

1. Tìm số tự nhiên x biết:

1) \(3^x.3=243\)

\(3^x=243:3\)

\(3^x=81\)

\(3^x=3^4\)

\(\Rightarrow x=4\)

_____

2) \(7.2^x=56\)

\(2^x=56:7\)

\(2^x=8\)

\(2^x=2^3\)

\(\Rightarrow x=3\)

_____

3) \(x^3=8\)

\(x^3=2^3\)

\(\Rightarrow x=3\)

_____

4) \(x^{20}=x\)

\(x^{20}-x=0\)

\(x\left(x^{19}-1\right)=0\)

\(\Rightarrow x=0\) hoặc \(x=1\)

5) \(2^x-15=17\)

\(2^x=17+15\)

\(2^x=32\)

\(2^x=2^5\)

\(\Rightarrow x=5\)

_____

6) \(\left(2x+1\right)^3=9.81\)

\(\left(2x+1\right)^3=729=9^3\)

\(\rightarrow2x+1=9\)

\(2x=9-1\)

\(2x=8\)

\(x=8:2\)

\(\Rightarrow x=4\)

_____

7) \(x^6:x^3=125\)

\(x^3=125\)

\(x^3=5^3\)

\(\Rightarrow x=5\)

_____

8) \(\left(2x-15\right)^5=\left(2x-15\right)^3\)

\(\rightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)

\(\left(2x-15\right)^3.\left[\left(2x-15\right)^2-1\right]=0\)

\(\Leftrightarrow\left\{{}\begin{matrix}\left(2x-15\right)^3=0\\\left(2x-15\right)^2-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{15}{2}\\x=7\\x=8\end{matrix}\right.\)

_____

9) \(3^{x+2}-5.3^x=36\)

\(3^x.\left(3^2-5\right)=36\)

\(3^x.\left(9-5\right)=36\)

\(3^x.4=36\)

\(3^x=36:4\)

\(3^x=9\)

\(3^x=3^2\)

\(\Rightarrow x=2\)

_____

10) \(7.4^{x-1}+4^{x+1}=23\)

\(\rightarrow7.4^{x-1}+4^{x-1}.4^2=23\)

\(4^{x-1}.\left(7+4^2\right)=23\)

\(4^{x-1}.\left(7+16\right)=23\)

\(4^{x-1}.23=23\)

\(4^{x-1}=23:23\)

\(4^{x-1}=1\)

\(4^{x-1}=4^1\)

\(\rightarrow x-1=0\)

\(x=0+1\)

\(\Rightarrow x=1\)

Chúc bạn học tốt

5.3^x = 5.3⁴

=> x = 4

5.3⁴ = 7.3⁵ - 2.3⁵

       = 3⁵ . (7 - 2)

       = 5. 3⁵

  => 3^x = 3⁵

=> x = 5

a) Ta có: \(5\cdot3^x=5\cdot3^4\)

\(\Leftrightarrow3^x=3^4\)

hay x=4

566 + 44 = 610

566/2 = 283

566+44= 610

566/2= 283

566+44=610

566:2=283

(tick mình nha)

1+5+7+48+5+2+5+5+566+54+4+4+54+54=814

5^4-3/100=1/20

3^3+2+1/3*13=3^5/13

5.3^7-5/5.3^5-3=1

2^15+14+13/2^13+12+11=2^6