2.log. ² x-log x³-9=0

2 log² x -  log x³  - 9 = 0 
2 log² x - 3 log x  - 9 = 0

log x = y
2y² - 3y - 9  = 0
(2y + 3)(y - 3) = 0
2y + 3 = 0  atau  y - 3 = 0
y = - 3/2   atau y = 3

log x = y
x = 10^y

y = - 3/2
x = (10)^(-3/2)
x = 1/(10√10)
x = (1/100) √10

y = 3 
x = 10³
x = 1.000