『Math』關於Function-----Completing the Square

let one number is x, then the other number is 10-x
sum of their square
=x^2+100-20x+x^2
=2x^2-20x+100
=2(x^2-10x+50)
differentiate x^2-10x+50
2x-10=0
x=5
so when x=5,the sum of their square is minimum
the two numbers are 5,5

x+y=10
10=
1+9
2+8
3+7
4+6
5+5
1+81=82
4+64=70---
25+25=50is minimum