Question

Решите уравнения за 8 класс

Answer 1

1.

$frac{2}{7} {x}^{2} - 3x + 9 = 0 : : : : | times 7 \ 2 {x}^{2} - 21x + 63 = 0 \ D = {( - 21)}^{2} - 4 times 2 times 63 = 441 - 504 = - 63$

Ответ: нет корней

2.

$frac{1}{2} {x}^{2} - 3x + frac{9}{2} = 0 : : : : | times 2 \ {x}^{2} - 6x + 9 = 0 \ D = {( - 6)}^{2} - 4 times 1 times 9 = 36 - 36 = 0 \ x = frac{6}{2} = 3$

Ответ: x = 3

3.

${y}^{2} - y - 30 = 0 \ D = {( - 1)}^{2} - 4 times 1 times ( - 30) = 1 + 120 = 121 \ sqrt{D} = sqrt{121} = 11 \ y_1 = frac{1 + 11}{2} = frac{12}{2} = 6 \ y_2 = frac{1 - 11}{2} = frac{ - 10}{2} = - 5$

Ответ: y1 = 6; y2 = -5