`#040911`
\(5^x\cdot5^{x+1}\cdot5^{x+2}=5^9?\)
\(\Rightarrow5^{x+x+1+x+2}=5^9\\ \Rightarrow5^{3x+3}=5^9\\ \Rightarrow3x+3=9\\ \Rightarrow3x=6\\ \Rightarrow x=6\div3\\ \Rightarrow x=2\)
Vậy, `x=2.`
5x . 5x + 1 . 5x + 2 = 59
5x + x + 1 + x + 2 = 59
x + x + 1 + x + 2 = 9
3x + 3 = 9
3x = 9 - 3
x = 6 : 3
x = 2
Vậy x = 2