If x^2 - 4x + 4b = 0 has two real solutions, find the value of 'b'.

A quadratic has real roots when its discriminant is ≥ 0. Here D = (−4)² − 4 × 1 × 4b = 16 − 16b ≥ 0, so b ≤ 1. (For two distinct real roots b < 1; b = 1 gives a repeated root.)