Question

Помогите решить #5 °° . Даю 20 баллов!!!

Answer 1

$y = {x}^{2} + 8x$

тогда

$y(y - 6) = 280 \ {y}^{2} - 6y - 280 = 0 \ y1 + y2 = 6 \ y1 times y2 = - 280 \ y 1= 20 \ y2 = - 14$

${x}^{2} + 8x = 20 \ {x}^{2} + 8x - 20 = 0 \ x1 times x2 = - 20 \ x1 + x2 = - 8 \ x1 = - 10 \ x2 = 2$

${x}^{2} + 8x = - 14 \ {x}^{2} + 8x + 14 = 0 \ d = 64 - 4 times 14 = 8 = 2 sqrt{2} \ x3 = frac{ - 8 - 2 sqrt{2} }{2} = - 4 - sqrt{2} \ x4 = - 4 + sqrt{2}$