Решите уравнение: а)3x²+5x-2=0 б)x²-2x-1=0 в)4x²-12x+9=0 заранее )

А) 3x² + 5x - 2 = 0
D = 25 + 4•2•3 = 25 + 24 = 49 = 7²
x1 = (-5 + 7)/6 = 2/6 = 1/3.
x2 = (-5 - 7)/6 = -12/6 = -2.

б) x² - 2x - 1 = 0
x² - 2x + 1 - 2 = 0
(x - 1)² - 2 = 0
(x - 1 - √2)(x - 1 + √2) = 0
x = 1 + √2
x = 1 - √2.

в) 4x² - 12x + 9 = 0
(2x)² - 2•2•3x + 3² = 0
(2x - 3)² = 0
2x = 3
x = 1,5.