Ta có : \(5+3x+1=86\)
\(\Leftrightarrow3x=86-5-1=80\)
\(\Leftrightarrow x=\frac{80}{3}\)
Vậy \(x=\frac{80}{3}\)
\(2008^x:2008^5=2008^3\)
\(\Leftrightarrow2008^{x-5}=2008^3\)
\(\Leftrightarrow x-5=3\Leftrightarrow x=8\)
Vậy \(x=8\)
\(6^x:12=3\)
\(\Leftrightarrow6^x=12\cdot3=36\)
\(\Leftrightarrow x=2\)
Vậy \(x=2\)
Bài làm :
\(1\text{)}5+3x+1=86\Leftrightarrow3x=80\Leftrightarrow x=\frac{80}{3}\)
\(2\text{)}2008^x\div2008^5=2008^3\Leftrightarrow2008^{x-5}=2008^3\Leftrightarrow x-5=3\Leftrightarrow x=8\)
\(3\text{)}6^x\div12=3\Leftrightarrow6^x=36\Leftrightarrow x=2\)
5 + 3 . x + 1 = 86
3 . x = 80
x vô nghiệm
2008x : 20085 = 20083
20083 x 20085
x = 3 x 5
x = 15
6x : 12 = 3
6x = 36
36 : 6 = 6
6 x 6 = 36
62 = 36
x = 2
