Question

若x^2+4y^2+2x-4y+2=0,求根号5x^2+16y^2的值.

Answer 1

x^2+2x+4y^2-4y+2=0

(x^2+2x+1)+(4y^2-4y+1)=0

(x-1)^2+(2y-1)^2=0

x=1,y=0.5

5x^2+16y^2

=5+4

=9

所以根号5x^2+16y^2的值为3.