Question

решение систем уравнений {x+3y=7
{x2+y =7

Answer 1

$\left \{ {{x+3y=7} \atop {x^2+y=7}} \right. \\y=7-x^2 \\x+3(7-x^2)=7 \\x+21-3x^2=7 \\-3x^2+x+14=0 \\3x^2-x-14=0 \\D=1+168=169=13^2 \\x_1= \frac{1+13}{6} = \frac{14}{6} = \frac{7}{3} \\x_2= \frac{1-13}{6} =-2 \\y_1=7-(\frac{7}{3} )^2=7- \frac{49}{9} = \frac{14}{9} \\y_2=7-4=3$
Ответ: (7/3;14/9), (-2;3)