Question

решите систему уравнений[ 7x-y=5
[ xy=18

Answer 1

$\left \{ {{7x-y=5} \atop {xy=18}} \right. \\x= \frac{18}{y} \\ \frac{7*18}{y} -y=5 \\y^2+5y-7*18=0 \\D=25+504=529=23^2 \\y_1= \frac{-5+23}{2} =9 \\y_2= \frac{-5-23}{2} =-14 \\x_1=2 \\x_2= \frac{18}{-14} =- \frac{9}{7}$
Ответ: (2;9), (-9/7;-14)

Answer 2

y=7x-5

7x²-5x-18=0
D=25+504=529
x1=5+23/14=28/14=2
x2=5-23/14=-18/14=-9/7
y1=14-5=9
y2=-9-5=-14