\(2.3^x+3^{x+2}=99\)
⇔ \(2.3^x+3^x.3^2=99\)
⇔ \(3^x.\left(2+3^2\right)=99\)
⇔ \(3^x.11=99\)
⇔ \(3^x=99:11\)
⇔ \(3^x=9\)
⇔ \(3^x=3^2\)
=> \(x=2\)
Vậy \(x=2.\)
Chúc bạn học tốt!
\(2.3^x+3^{x+2}=99\)
\(\Leftrightarrow2.3^x+3^x.3^2=99\)
\(\Leftrightarrow3^x.\left(2+3^2\right)=99\)
\(\Leftrightarrow3^x.11=99\)
\(\Leftrightarrow3^x=\frac{99}{11}\)
\(\Leftrightarrow3^x=9=3^2\)
\(\Leftrightarrow x=2\)
Vậy : \(x=2\)
\(2.3^x+3^{x+2}=99\)
\(\Leftrightarrow2.3^x+3^x+3^2=99\)
\(\Leftrightarrow2.3^x+9.3^x=99\)
\(\Leftrightarrow\left(2+9\right).3^x=99\)
\(\Leftrightarrow11.3^x=99\)
\(\Leftrightarrow3^x=9\)
\(\Leftrightarrow x=2\)
