Question

用作差法比较大小x^2+y^2+1 与 x+y+xy 注:x^2即为x的平方,y同理.

Answer 1

x^2+y^2+1 -x-y-xy=(x-1/2）^2-1/4+(y-1/2)^2-1/4-xy+1==(x-1/2）^2+(y-1/2)^2-xy+1/2