№1.
1) x∈R
2)18 - 6x ≥ 0
6x ≤ 18
x ≤ 3
3) 9 - x² ≠ 0
x ≠ -3 и x ≠ 3
№2
1) 16 - 12 = √(2x/3)
4 = √(2x/3)
16 = 2x/3
48 = 2x
x = 24
2) 1 + x² + 2x = 1 + x√(x² + 12)
x(x + 2 - √(x² + 12)) = 0
x1 = 0
x + 2 = √(12 + x²)
x² + 4x + 4 = 12 + x²
4x = 8
x = 2
3) x ≥ -4/7
12 + x = 7x + 8 + 4 - 4√(7x+8)
4√(7x+8) = 6x
28x + 32 = 9x²
9x² - 28x - 32 = 0
D = 784 + 1152 = 1936
x1 = (28 - 44)/18 = -16/18 = -8/9 < -4/7
x2 = (28 + 44)/18 = 72/18 = 4
Ответ: 4
4) 0 ≤ 9 - x ≤ 9
-9 ≤ -x ≤ 0
0 ≤ x ≤ 9 - ответ