f. 4 maths

希望識既人可以解答下我啦~ thanks!!
同埋可唔可以譯返句野既中文比我知??

Given that the sum of two numbers is 20, find the minimum value of the sum of the squares of these two numbers.

Given that the axis of symmetry of y = x^2 + 2kx + k is  x + 4=0, find the optimum value of the function.

thanks a lot!

[[i] 本帖最後由 -cathy 於 2006-11-2 08:53 PM 編輯 [/i]]

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

[quote]原帖由 [i]牙盈''[/i] 於 2006-11-2 08:14 PM 發表
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 ... [/quote]
wow@@ 好勁呀 !! thx a lot :em32:

[quote]原帖由 [i]牙盈''[/i] 於 2006-11-2 08:14 PM 發表
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 ... [/quote]
咁我想問咩係 sq ?_?

呀 XD

square =)