Помогите решить задания по алгебре (огэ номер 21)

1. 18^[n] / (3^[2n-1] * 2^[n-2]) = 2^[n] * 9^[n] / (3^[2n-1] * 2^[n-2]) = 2^[n] * 3^[2n] / (3^[2n-1] * 2^[n-2]) =
= 2² * 3 = 12.

2. 1,5x² - 2x -2 = 0
3x² - 4x - 4 =0
D= 16+48 = 64 = 8²
x = (4 ± 8) / 6
x1 = 2; x2 = -2/3.

3. { (24-3x)/(8+(5-2x)²) >= 0; 22 - 9x =< 43 - 2x} =>
{ (8-x)/(8+(5-2x)²) >= 0; 7x >= -21} =>
{ 8 >= x; x>=-3} => -3 <= x <= 8.

4. p(b) = (b+3/b)(3b+1/b)
p(1/b) = (1/b + 3b)(3/b + b).
p(b)/p(1/b) = 1.

5. (x³+4x²-9x-36)/((x-3)(x+4)) = (x²-9)(x+4)/((x-3)(x+4)) = (x-3)(x+3)(x+4)/((x-3)(x+4)) = x+3.

6. { (2x+6y)²=8y, (2x+6y)²=8x} => {8y-8x=0, (2x+6y)²=8x} => {x=y, (8x)²=8x} =>
[{x=0, y=0}, {x=1/8, y=1/8}].

7. ((4x)³ * x^[-11]) / (x^[-12] * 5 * x^[5]) = 64/5 * x^[3-11+12-5] = 12.8/x = {x=2} = 6.4

8. {3x-y=15, (x+6)/2 - y/3 =6} => {y= 3x-15, (x+6) - 2(x-5)=12} => {x=4, y=-3}.

9. Совпадает с №3.

10. x² = t =>
t²+2t-8 = 0
D= 4+32 = 6²
t = (-2 ± 6)/2 = -1±5
t>=0 => t=4
=> x = ±2.

Здесь с 1 по 10.
N 21 здесь нет.

не видно