Question

Tìm x

3^x + 3^x+2 = 90

sẽ tick

Answer 1

\(3^x+3^{x+2}=90\)

\(\Rightarrow3^x+3^x.3^2=90\)

\(\Rightarrow3^x+3^x.9=90\)

\(\Rightarrow3^x\left(1+9\right)=90\)

\(\Rightarrow3^x.10=90\)

\(\Rightarrow3^x=\dfrac{90}{10}\)

\(\Rightarrow3^x=9\Rightarrow3^x=3^2\Rightarrow x=2\)

Answer 2

Ta có:

3^x + 3^{x + 2} = 90

=> 3^x + 3^x . 3² = 90

=> 3^x.(1 + 3²) = 90

=> 3^x.(1 + 9 ) = 90

=> 3^x .10 = 90

=> 3^x = 90:10=9

=> 3^x= 3²=> x = 2

Vậy x = 2

Answer 3

\(3^x+3^{x+2}=90\\ \Leftrightarrow3^x+3^x\cdot3^2=90\\\Leftrightarrow 3^x\left(1+3^2\right)=90\\ \Leftrightarrow3^x\cdot10=90\\ \Leftrightarrow3^x=9\\ \Leftrightarrow3^x=3^2\\ \Leftrightarrow x=2\)

Vậy \(x=2\)

Answer 4

\(3^x+3^{x+2}=90\)

\(\Rightarrow3^x.1+3^x.3^2=90\)

\(\Rightarrow3^x.1+3^x.9=90\)

\(\Rightarrow3^x\left(1+9\right)=90\)

\(\Rightarrow3^x.10=90\)

\(\Rightarrow3^x=9\)

\(\Rightarrow x=2\)