№6
log₂ (9 - x) = 2log₂3
log₂ (9 - x) = log₂3²
log₂ (9 - x) = log₂9
9 - x = 9
x = 0
№7
log₅ (x² + 4x) = log₅ (x² + 11)
x² + 4x = x² + 11
4x = 11
x = 11/4
№8
log₃ (7 + 2x) = log₃ (3 - 2x) + 2
log₃ (7 + 2x) = log₃ (3 - 2x) + log₃ 9
log₃ (7 + 2x)= log₃ ((3 - 2x) * 9)
log₃ (7 + 2x) = log₃ (27 - 18x)
7 + 2x = 27 - 18x
18x + 2x = 27 - 7
20x = 20
x = 1
№9
logₓ₋₂ 16 = 2
(x - 2)² = 16
1) (x - 2)² = 4²
x - 2 = 4
x = 4 + 2
x = 6
2) (x - 2)² = -4²
x - 2 = - 4
x = - 4 + 2
x = - 2
Ответ: -2.