Question

已知x^2+y^2-8x+2y+17=0,求x+y的值

Answer 1

x^2+y^2-8x+2y+17=0

得(x-4)^2+(y+1)^2=0

因为(x-4)^2>=0

(y+1)^2>=0

所以x-4=0

y+1=0

x=4

y=-1

x+y=3