\(3^x+5.3^{x-1}=72\)

=> \(3^{x-1}.3+5.3^{x-1}=72\)

=> \(3^{x-1}.\left(3+5\right)=72\)

=> \(3^{x-1}.8=72\)

=>  \(3^{x-1}=72:8\)

=>  \(3^{x-1}=9\)

=>   \(3^{x-1}=3^2\)

=>      \(x-1=2\)

=>             \(x=2+1\)

=>             \(x=3\)

          Chúc học tốt 

\(9^{x+1}-5.3^{2x}=72\)

\(\rightarrow9^x.9-5.\left(3^2\right)^x=72\)

\(\rightarrow9^x.9-5.9^x=72\)

\(\rightarrow9^x\left(9-5\right)=72\)

\(\rightarrow4.9^x=72\)

\(\rightarrow9^x=18\)

\(\Rightarrow x=1,315...\)

Vậy \(x=1,315...\)

1)Tính:

4.{624:[5+7.(72:2³-6)]}-5.3

=4.{624:[5+7.(72:8-6]}-15

=4.{624:[5+7.(9-6)]}-15

=4.{624:[5+7.3]}-15

=4.{624:26}-15

=4.24-15

=81

2) Tìm x biết

a)108-x=32.7

108-x=224

x=108-224

x=-116

b)15-(5x-4):3=23

(5x-4):3=15-23

(5x-4):3=-8

5x-4=-8.3

5x-4=-24

5x=-24+4

5x=-20

x=-20:5

x=-4

Bài 1 :

4 . {624 :[5 + 7 . (72 : 2³ - 6)]} - 5 . 3

= 4 . {624 :[ 5 + 7 . (72 : 8 - 6)]} - 15

= 4 . {624 : [5 + 7 . (9 - 6)]} - 15

= 4 . [624 : (5 + 7 . 3)] - 15

= 4 . [624 : (5 + 21)] - 15

= 4 . (624 : 26) - 15

= 4 . 24 - 15

= 96 - 15

= 81

1)

\(4.\left\{624:\left[5+7.\left(72:2^3-6\right)\right]\right\}-5.3\)

\(=4\left\{624:\left[5+7.\left(72:8-6\right)\right]\right\}-15\)

\(=4.\left\{624:\left[5+7.\left(7-6\right)\right]\right\}-15\)

\(=4\left\{624:\left[5+7.1\right]\right\}-15\)

\(=4.\left\{624:\left[5+7\right]\right\}-15\)

\(=4.\left\{624:12\right\}-15\)

\(=4.52-15\)

\(=208-15=193\)

Bài 2 :

a) \(108-x=32.7\)

\(108-x=224\)

\(x=108-224\)

\(x=-116\)

Vậy \(x=-116\) là giá trị cần tìm

b) \(15-\left(5x-4\right):3=23\)

\(\left(5x-4\right):3=15-23\)

\(\left(5x-4\right):3=-8\)

\(5x-4=\left(-8\right).3\)

\(5x-4=-24\)

\(5x=\left(-24\right)+4\)

\(5x=-20\)

\(x=-20:5\)

\(x=-4\)

Vậy \(x=-4\) là giá trị cần tìm

b) 3.[5^2x+1 - (5²)^x] = 3.100

3( 5^2x+1-5^2x) = 3.100

-> 5^2x+1-5^2x = 100

mà 5³-5²= 100

-> 5^2x+1-5^2x = 5³-5²

^{Vậy x = 1}

c) (4²)^x : 4^x = 4²

<=>4^2x-x =4²

<=> 4^x = 4²

-> x=2

d) 2^x( 0,5 +4) = 72

2^x. 4,5 = 72

2^x = 72:4,5 = 16

2^x = 2⁴ = 16

-> x= 4

=0 nhe

3^x-1+5.3^x-1=162

3^x-1.(1+5)=162

3^x-1.6=162

3^x-1=162:6

3^x-1=27

3^x-1=3^3

x-1=3

x=3+1

x=4

3^x-1 +5.3^x-1=162

6. 3^x-1=162

3^x-1=27

x-1=3

x=4

\(3^{x-1}\)+5.\(3^{x-1}\)=162

\(\Leftrightarrow\)\(3^{x-1}\)(1+5)=162

\(\Leftrightarrow\)\(3^{x-1}\)=27

\(\Leftrightarrow\)\(3^{x-1}\)=3³

^{\(\Leftrightarrow\)}x-1=3

\(\Leftrightarrow\)x=4

Vậy x=4

Ta có : 3^{x - 1} + 5 . 3^{x - 1} = 162

 \(\Leftrightarrow\)3^{x - 1} . ( 1 + 5 ) = 162

\(\Leftrightarrow\)3^{x - 1} . 6 = 162

\(\Leftrightarrow\)3^{x - 1}  = 162 ÷ 6 = 27

\(\Leftrightarrow\)3^{x - 1} = 3³

\(\Leftrightarrow\)x - 1 = 3

\(\Leftrightarrow\)x = 4

Vậy : x = 4