Question

已知x^2+y^2+10=2x+6y则x^21+21y的值为

Answer 1

(x^2-2x+1)+(y^2-6y+9)=0

(x-1)^2+(y-3)^2=0

平方相加为0则都等于0

所以x-1=0,y-3=0

x=1,y=3

所以x^21+21y=1+63=64