Find the minimum value of A=x^2 + y^2 if x + y =10
问题描述：
Find the minimum value of A=x^2 + y^2 if x + y =10
答
A=x^2 + y^2
= x^2+(10-x)^2
=2x^2-20x+100
when x=5 A is minimun,that is 50