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\(3^{x+2}+4\cdot3^{x+1}=7\cdot3^6\)

\(3\cdot3^{x+1}+4\cdot3^{x+1}=7\cdot3^6\)

\(\left(3+4\right)\cdot3^{x+1}=7\cdot3^6\)

\(7\cdot3^{x+1}=7\cdot3^6\)

x + 1 = 6

x = 6 - 1 = 5

Vậy x = 5

\(7\cdot3^{x-1}-3^{x+2}=540\)

=>\(7\cdot3^x\cdot\dfrac{1}{3}-3^x\cdot9=540\)

=>\(3^x\left(\dfrac{7}{3}-9\right)=540\)

=>\(3^x\cdot\dfrac{-20}{3}=540\)

=>\(3^x=-540:\dfrac{20}{3}=-540\cdot\dfrac{3}{20}=-27\cdot3=-81\)

=>\(x=log_3\left(-81\right)\)

4² . x -1 = 7.3²

16 . x - 1= 7.9

16 . x -1 = 63

16 . x = 63 + 1

16 . x = 64

x = 64 : 16

x = 4

4².x-1=7.3²

16.x-1=7.9

16.x-1=63

16.x=63+1

16.x=64

x=64:16

x=4

3^x+2 + 4.3^x+1 = 7.3⁶

3^x+1.(3 + 4) = 7.3⁶

3^x+1.7 = 7.3⁶

=> 3^x+1 = 3⁶

=> x + 1 = 6

=> x = 5

lớp 7 mà mình ấn nhằm

Đáp án:

13. -12(x-5)+7(3-x)=5

      -12x-(-12).5+7.3-7x=5

       -12x-(-60)+21-7x=5

       -12x+60+21-7x=5

       -12x+(60+21)-7x=5

        -12x-7x+81=5

        -19x+81     =5

        -19x            =5-81

        -19x            =-76

              x            =(-76):(-19)

              x            =4

Vậy x=4.

viết thế này thánh hiểu

3^x + 2 + 4.3 +1 = 7.3^6

3^x + 2 + 12 + 1 = 21^6

3^x + 15 = 21^6

ko làm được nữa thì hịu

\(7\cdot3^{x-1}-3^{x+2}=-540\)

\(\Leftrightarrow3^x\left[7\cdot\left(-3\right)-3^2\right]=-540\)

\(\Leftrightarrow3^x\cdot\left(-30\right)=-540\)

\(\Leftrightarrow3^x=18\)

Ta có : \(7.3^{x-1}-3^{x+2}=-540\)

\(\Leftrightarrow\left(7-3^3\right).3^{x-1}=-540\)

\(\Leftrightarrow\left(7-27\right).3^{x-1}=-540\)

\(\Leftrightarrow-20.3^{x-1}=-540\)

\(\Leftrightarrow3^{x-1}=\left(-540\right):\left(-20\right)\)

\(\Leftrightarrow3^{x-1}=27\)

\(\Leftrightarrow3^{x-1}=3^3\Rightarrow x-1=3\Rightarrow x=4\)

Vậy \(x=4\)

Lời giải:

1.

$3^{x+2}+4.3^{x+1}=7.3^6$

$3^{x+1}.3+4.3^{x+1}=7.3^6$

$3^{x+1}(3+4)=7.3^6$

$3^{x+1}.7=7.3^6$

$\Rightarrow 3^{x+1}=3^6$

$\Rightarrow x+1=6$

$\Rightarrow x=5$

2.

$5^{x+4}-3.5^{x+3}=2.5^{11}$

$5^{x+3}.5-3.5^{x+3}=2.5^{11}$

$5^{x+3}(5-3)=2.5^{11}$

$2.5^{x+3}=2.5^{11}$

$\Rightarrow 5^{x+3}=5^{11}$

$\Rightarrow x+3=11$

$\Rightarrow x=8$

3.

$4^{x+3}-3.4^{x+1}=13.4^{11}$

$4^{x+1}.4^2-3.4^{x+1}=13.4^{11}$

$4^{x+1}.16-3.4^{x+1}=13.4^{11}$

$13.4^{x+1}=13.4^{11}$

$\Rightarrow 4^{x+1}=4^{11}$

$\Rightarrow x+1=11$
$\Rightarrow x=10$