Răspuns:
a) 2x² - 5x = x (2x - 5)
b) x² - 4 = (x - 2)(x + 2)
c) a² - 4a + 4 = (a - 2)(a - 2)
d) 4x² - 9 = (2x - 3)(2x + 3)
e) y² - 36/49 = (y - 6/7)(y + 6/7)
f) 25a² - 20a + 4 = (5a - 2)(5a - 2)
a² - b² = (a + b)(a - b)
a² ± 2ab + b² = (a ± b)² = (a ± b)(a ± b)
