個問題大概問你 ..     有 2 個數 ..   SUM 係 20
你要搵番呢兩個數既 SQ 既 MIN. VALUE ..

Let x be one of the number
      y be sum of their sq

x^2 + (20-x)^2 = y
x^2 + (400 - 40x + x^2)
2x^2 - 40x + 400
2 (x^2 - 20x) + 400
2 ( x^2 - 20x + 10^2 - 10^2 ) + 400
2 ( x - 10 )^2 - (2) (10^2) + 400
2 ( x - 10 )^2 + 200

so the min. value is 200 .

我都唔知o岩唔o岩 = v =
試下啦 XDDD

呀 XD

square =)