Verified answer

1) x² - 81 = 0

x² = -c/a

x = √-c/a

x = ✓81/1

x = +-9

Ответ : x1 = 9 ; x2 = -9

2) 2x² - 3x = 0

x (2x - 3) = 0

x = 0

x = -b/a

x = 3/2

x = 1,5

Ответ : x1 = 0 ; x2 = 1,5