Question

Решите систему уравнений:
{x-4y=3
{x²-21y=28

Answer 1

Подстановка
x = 4y + 3
(4y + 3)^2 - 21y = 28
16y^2 + 24y + 9 - 21y - 28 = 0
16y^2 + 3y - 19 = 0
(y - 1)(16y + 19) = 0
y1 = 1; x1 = 4y + 3 = 4*1 + 3 = 7
y2 = -19/16; x2 = 4y + 3 = -19/4 + 3 = -19/4 + 12/4 = -7/4
Ответ: (7; 1); (-7/4; -19/16)