a)7.2^x=56⇔2^x=8⇔2^x=2³⇔x=3

b)(2x+1)³=9.81⇔(2x+1)³=9³⇔2x+1=9⇔2x=8⇔x=4

c)x³=8²⇔x³=2⁶⇔x=2²⇔x=4

d)4.2^x-3=1⇔4.2^x=4⇔2^x=1⇔2^x=2⁰⇔x=0

e)2.3^x=162⇔3^x=81⇔3^x=3⁴⇔x=4

`4^(x+2) .3^x = 16.12^5`

`4^(x+2) .3^x = 4^2 . (3.4)^5`

`4^(x+2) .3^x = 4^2 . 3^5. 4^5`

`4^(x+2) .3^x = 4^7 . 3^5`

`4^(x+2) .3^x = 4^(5+2) . 3^5`

`x=5`

Ta có:4^x+2.3^x=16.12⁵

     ⇔ 4^x+2.3^x=4¹⁷.3¹⁵

      ⇔ 4^x+2:4¹⁷.3^x:3¹⁵=1

     ⇔ 4^x-15.3^x-15=1

     ⇔ 12^x-15=12⁰

     ⇔ x-15=0

     ⇔ x=15

Ta có: \(4^{x+2}\cdot3^x=16\cdot12^5\)

\(\Leftrightarrow4^x\cdot16\cdot3^x=16\cdot12^5\)

\(\Leftrightarrow12^x=12^5\)

hay x=5

\(2.3^x=10.3^{12}+8.\left(3^3\right)^4\)

\(2.3^x=10.3^{12}+8.3^{12}\)

\(2.3^x=3^{12}.\left(10+8\right)\)

\(2.3^x=3^{12}.18\)

\(3^x=3^{12}.18:2\)

\(3^x=3^{12}.9\)

\(3^x=3^{12}.3^2\)

\(3^x=3^{14}\)

\(\Rightarrow x=14\)

2.3^x=10.3¹²+8.27⁴

2.3^x=10.3¹²+2³.3¹²

2.3^x=3¹².18

2.3^x=3¹².3².2

2.3^x=3¹⁴.2

=>x=14

\(2.3^{x+3}=10.3^{12}+8.3^{12}\)

\(\Leftrightarrow2.3^{x+3}=18.3^{12}\)

\(\Leftrightarrow3^{x+3}=9.3^{12}\)

\(\Leftrightarrow3^{x+3}=3^{14}\)

\(\Leftrightarrow x+3=14\Leftrightarrow x=11\)

\(\Leftrightarrow2\cdot3^{x+3}=3^{12}\cdot18\\ \Leftrightarrow2\cdot3^{x+3}=3^{14}\cdot2\\ \Leftrightarrow x+3=14\Leftrightarrow x=11\)

2.3x+3=10.312+8.3122.3x+3=10.312+8.312

=2.3x+3=18.312⇔2.3x+3=18.312

=3x+3=9.312⇔3x+3=9.312

=3x+3=314⇔3x+3=314

\(2.3^x+5.3^x.3=153\Leftrightarrow2.3^x+15.3^x=153\)

\(\Leftrightarrow17.3^x=153\Leftrightarrow3^x=9\Leftrightarrow x=2\)

\(\Leftrightarrow2.3^x+5.3.3^x=153\)

\(\Leftrightarrow17.3^x=3^2.17\)

\(\Leftrightarrow3^x=3^2\Rightarrow x=2\)

Bạn xem lại đề

2.3^x=10.3¹²+8.27⁴

2.3^x=10.3¹²+2³.3¹²

2.3^x=3¹².18

2.3^x=3¹².3².2

2.3^x=3¹⁴.2

=>x=14

mỏi cả tay 

Ta có: \(4.3^{x+2}-2.3^{x+1}=810\)

\(4.3^{x+1}.3-2.3^{x+1}=810\)

\(2.3^{x+1}\left(2.3-1\right)=810\)

\(2.3^{x+1}.5=810\)

\(3^{x+1}=81=3^4\)

x+1=4

x=3

\(2.3^{x+1}=10.3^{12}+8.3^{12}\\ VP=\left(10+8\right).3^{12}=18.3^{12}=2.3^2.3^{12}\\ =2.3^{2+12}=2.3^{14}\\ VT=VP\\ \Rightarrow2.3^{x+1}=2.3^{14}\\ \Rightarrow x+1=14\\ Vậy:x=14-1=13\)

2.3ˣ⁺¹ = 10.3¹² + 8.3¹²

2.3ˣ⁺¹ = 3¹².(10 + 8)

2.3ˣ⁺¹ = 3¹².18

3ˣ⁺¹ = 3¹².18 : 2

3ˣ⁺¹ = 3¹².9

3ˣ⁺¹ = 3¹².3²

3ˣ⁺¹ = 3¹⁴

x + 1 = 14

x = 14 - 1

x = 13

\(2\cdot3^{x+1}=10\cdot3^{12}+8\cdot3^{12}\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot(10+8)\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot18\\\Rightarrow 2\cdot3^{x+1}=3^{12}\cdot3^2\cdot2\\\Rightarrow 3^{x+1}=3^{12}\cdot3^2\\\Rightarrow 3^{x+1}=3^{14}\\\Rightarrow x+1=14\\\Rightarrow x=14-1\\\Rightarrow x=13\\Vậy:x=13\)

Chọn C

-1/2.3x+3/4=-2.25

-1/2.3x+3/4=9/4

-1/2.3x      =9/4-3/4

-1/2.3x      =3/2

       3x     =3/2:-1/2

       3x     =-3

        x     =-3:3

        x     =-1

vậy   x=-1

\(-\frac{1}{2}.3x+\frac{3}{4}=-2,25\)

\(\Rightarrow\frac{1}{2}.(-3).x+\frac{1}{2}.\frac{3}{2}=\frac{9}{4}\)

\(\Rightarrow\frac{1}{2}.\left(-3x+\frac{3}{2}\right)=\frac{9}{4}\)

\(\Rightarrow-3x+\frac{3}{2}=\frac{9}{4}:\frac{1}{2}\)

\(\Rightarrow-3x+\frac{3}{2}=\frac{9}{2}\)

\(\Rightarrow-3x=3\)

\(\Rightarrow x=-1\)