a) Ta có: \(81=3^4\)
\(\Rightarrow3^x=3^4\)
Vậy x = 4
b) Ta có: \(49=7^2\)
\(\Rightarrow7^{x-9}=7^2\)
\(\Rightarrow x-9=2\)
\(\Rightarrow x=2+9=11\)
Vậy x = 11
Ủng hộ tớ nha!
a) 3x = 81
3x = 34
=> x = 4
Vậy x = 4
b) 7x-9 = 49
7x-9 = 72
=> x - 9 = 2
x = 2 + 9
x = 11
Vậy x = 11
Ủng hộ mk nha !!!!
\(a.3^x=81\)
\(\Rightarrow3^x=3^4\)
\(\Rightarrow x=4\)
\(b.7^{x-9}=49\)
\(7^{x-9}=7^2\)
\(\Rightarrow x-9=2\)
\(\Rightarrow x=2+9=18\)
