Show that 4x² - 20x + 25 = 0 has only one solution.

First method

4x² - 20x + 25 = 0

(2x - 5)² = 0

x = 5 / 2

Second method

4x² - 20x + 25 = 0

a = 4, b = -20 and c = 25

b² = 400

4ac = 400

b² = 4ac

-b / (2a) = 5 / 2