a.

123-5.(x+4)=38

=>5.(x+4)=123-68

=>5.(x+4)=85

=>x+4=85:5

=>x+4=17

=>x=17-4

=>x=13

b. (3.x-2⁴).7³=2.7⁴

=>3.x-16=2.7⁴:7³

=>3.x-16=14

=>3.x=14+16

=>3.x=30

=>x=30:3

=>x=10

\(12^8:2^8< =6^x< =\left(6^3\right)^3\)

<=> \(1679616< =6^x< =6^9\)

<=> \(6^8< =6^x< =6^9\)

<=> \(8< =x< =9\)

a)

6^x : 12 = 3

6^x = 3 . 12

6^x = 36

6^x = 6²

=> x = 2

b) 2 . 3^x - 5 = 7²

   2 . 3^x - 5 = 49

    2 . 3^x = 49 + 5

   2 . 3^x = 54

    3^x = 54 : 2

    3^x = 27

     3^x = 3³

    => x = 3

\(\left(19x+2.5^2\right):14=\left(13-8\right)^2-4^2\)

<=> \(\left(19x+50\right):14=25-16\)

<=> \(\left(19x+50\right):14=9\)

<=> \(19x+50=126\)

<=> \(19x=76\)

<=> \(x=4\)

câu B làm j có \(x\)để tìm

\(390-\left(x-7\right)=169:13\)

<=> \(390-x+7=13\)

<=> \(390-x=6\)

<=> \(x=384\)

\(x-6:2-\left(48:24\right):2:6-3=0\)

<=> \(x-3-2:2:6=3\)

<=> \(x-3-\frac{1}{6}=3\)

<=> \(x=\frac{37}{6}\)

\(x+5.2-\left(32+16.3:6-15\right)=0\)

<=> \(x+10-25=0\)

<=> \(x=15\)

2 . 3^x = 10 . 3¹² . 8 . 27⁴

1/ 2.x²⁰¹² = x²⁰¹⁴ 

<=> 2.x²⁰¹² - x²⁰¹⁴ = 0

<=> x²⁰¹² . ( 2 - 1) = 0

<=> x²⁰¹² . 1 = 0

<=> x²⁰¹² = 0

<=> x = 0

    Vậy x = 0

2/ 2^x-1 .8 + 2^{x - 1} .3 = 44

<=> 2^x-1 . ( 8 + 3 ) = 44

<=> 2^x-1 . 11 = 44

<=> 2^x-1    = 44  : 11

<=> 2^x-1    = 4

<=>  2^x-1   = 2² 

<=> x - 1 = 2

<=>   x    = 3

     Vậy x = 3

3/ 2² . 3^x = 108

<=> 4 . 3^x = 108

<=>   3^x    = 108 : 4

<=>    3^x   = 27

<=> 3^x      = 3³

<=>   x      = 3

      Vậy x = 3

     ~ Hok tốt ~

a. \(\left(\frac{8}{27}\right)^x=\left(\frac{2}{3}\right)^{72}\)

\(\left(\frac{2}{3}\right)^{3x}=\left(\frac{2}{3}\right)^{72}\)

\(\Rightarrow3x=72\Rightarrow x=24\)

Vậy x = 24 

\(a,\left(7x-11\right)^3=2^5.5^2+200.\)

\(\left(7x+11\right)^3=32.25+200.\)

\(\left(7x+11\right)^3=800+200.\)

\(\left(7x-11\right)^3=1000.\)

\(\left(7x-11\right)^3=10^3.\)

\(\Rightarrow7x-11=10.\)

\(\Rightarrow x=\left(10+11\right):3=7\in Z.\)

Vậy.....

\(b,3^x+25=26.2^2+2.3^0.\)

\(3^x+25=26.4+2.\)

\(3^x+25=104+2.\)

\(3^x+25=106.\)

\(3^x=106-25.\)

\(3^x=81.\)

\(3^x=3^4\Rightarrow x=4\in Z.\)

Vậy.....

\(c,2^x+3.2=64.\)(có vấn đề).

\(d,5^{x+1}+5^x=750.\)

\(5^x.5^1+5^x+1=750.\)

\(5^x\left(5^1+1\right)=750.\)

\(5^x\left(5+1\right)=750.\)

\(5^x.6=750.\)

\(5^x=750:6.\)

\(5^x=125.\)

\(5^x=5^3\Rightarrow x=3\in Z.\)

Vậy.....

\(e,x^{15}=x.\)

\(\Rightarrow x\left(x^{14}-1\right)=0\Rightarrow\left\{{}\begin{matrix}x=0\\x=1\end{matrix}\right..\)

\(f,\left(x-5\right)^4=\left(x-5\right)^6.\)

\(\Leftrightarrow\left(x-5\right)^4-\left(x-5^6\right)=0.\)

\(\Leftrightarrow\left(x-5\right)^4\left[1-\left(x-5\right)^2\right]=0.\)

\(\Leftrightarrow\left(x-5\right)^4\left(1-x+5\right)\left(1+x-5\right)=0.\)

\(\Leftrightarrow\left(x-5\right)^4\left(6-x\right)\left(x-4\right)=0.\)

\(\Leftrightarrow\left(x-5\right)^4=0\Rightarrow x-5=0\Rightarrow x=5\in Z.\)

\(6-x=0\Rightarrow x=6\in Z.\)

\(x-4=0\Rightarrow x=4\in Z.\)

Vậy.....