Question

若x^2+6y^2-4xy-4y+2=0,求x^2+y^2的值

Answer 1

x²+6y²-4xy-4y+2=0

(x²-4xy+4y²)+(2y²-4y+2)=0

(x-2y)²+2(y-1)²=0

y-1=0 y=1

x-2y=0 x=2y=2

x²+y²=4+1=5