Question

x的平方-3xy-10y的平方=18,x+2y=2,求x,y的值

Answer 1

{x^2-3xy-10y^2=18,①

{x=2-2y.②

把②代入①,得

(2-2y)^2-3y(2-2y)-10y^2=18,

4-8y+4y^2

.-6y+6y^2

...-10y^2=18,

-14y=14,y=-1.

代入②,x=4.