Question

Решите x(квадрате)-3x-4=0

Answer 1

${x}^{2} - 3x - 4 = 0$
a = 1, b = -3, c = -4
D = b^2 - 4ac = 9 - 4*(-4) = 9 + 16 = 25
$x1 = \frac{ - b + \sqrt{d} }{2a} = \frac{3 + 5}{2} = \frac{8}{2} = 4 \\ x2 = \frac{ - b - \sqrt{d} }{2a} = \frac{3 - 5}{2} = \frac{ - 2}{2} = - 1$
Ответ: -1; 4.