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

First method

25x² - 20x + 4 = 0

(5x - 2)² = 0

x = 2 / 5

Second method

25x² - 20x + 4 = 0

a = 25, b = -20 and c = 4

b² = 400

4ac = 400

b² = 4ac

-b / (2a) = 2 / 5