``` 9) { (x + 3y)(y² + 2) + 2(3x + y) = 4(0y² + 4) (3x + y)(2x² + 1) = x + 3y + 8x². 10) { 5x(y² - 4) = 8(x² + y²) 5y(x² + 4) = 6(x² + y²). 11) { x³ + y³ = 91 4x² + 3y² = 16x + 9y. 12) { x + 3y = x³ - 12 -y + 4z = y³ - 6 9z + 2x = z³ + 32. ```
----- Nội dung ảnh -----
```
9)
{ (x + 3y)(y² + 2) + 2(3x + y) = 4(0y² + 4)
(3x + y)(2x² + 1) = x + 3y + 8x².
10)
{ 5x(y² - 4) = 8(x² + y²)
5y(x² + 4) = 6(x² + y²).
11)
{ x³ + y³ = 91
4x² + 3y² = 16x + 9y.
12)
{ x + 3y = x³ - 12
-y + 4z = y³ - 6
9z + 2x = z³ + 32.
```