А) 7x^2 - 28 = 07x^2 = 28x^2 = 28/7x^2 = 4x = ±2
Б) x^2 + 20x + 91 = 0(x + 13)(x + 7) = 0x + 13 = 0 or x + 7 = 0x = -13 or x = -7
В) 7x^2 - 9x + 2 = 0(7x - 2)(x - 1) = 07x - 2 = 0 or x - 1 = 0x = 2/7 or x = 1
Г) 5x^2 = 12x5x^2 - 12x = 0x(5x - 12) = 0x = 0 or x = 12/5
А) 7x^2 - 28 = 0
7x^2 = 28
x^2 = 28/7
x^2 = 4
x = ±2
Б) x^2 + 20x + 91 = 0
(x + 13)(x + 7) = 0
x + 13 = 0 or x + 7 = 0
x = -13 or x = -7
В) 7x^2 - 9x + 2 = 0
(7x - 2)(x - 1) = 0
7x - 2 = 0 or x - 1 = 0
x = 2/7 or x = 1
Г) 5x^2 = 12x
5x^2 - 12x = 0
x(5x - 12) = 0
x = 0 or x = 12/5