If x⁴ - 5x² + 4 = 0; the values of x are :

1. 1 or 2

2. ± 1 or ± 2

3. -1 and 2

4. -2, -1, 1 or 2

The product of two integers is -18; the integers are :

1. -2 and 9 or -9 and 2

2. -6 and -3 or 6 and 3

3. -9 and -2 or 9 and 2

4. 1 and 18 or 18 and 1.

Solve :

2x⁴ - 5x² + 3 = 0