Use quadratic formula to solve:

x² = 4x

From each of the following equations, find the value of constant 'k' so that each equation has real and equal roots.

(i) kx(x - 2) + 6 = 0

(ii) (k + 4)x² + (k + 1)x + 1 = 0

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