三角學(20點) - Ans.fyi 參考答案

三角學(20點)

匿名

2011-06-19 8:00 pm

按右鍵「另存圖片」再開啟會睇到清楚d教我做圈住咗嘅題目…唔該哂答案 :22. (b) 30度23. (a) 15/16 (b) 17/1624. (b) (x-1)(2x-1)(3x-1) (c) 0,60,70.5,289.5,300,360度25. (a) 2(x-1/2)^2 + 6 (b) 6 (c) 60,300度

圖片參考：http://imgcld.yimg.com/8/n/HA00230702/o/701106190031813873461170.jpg

更新1:

25. (a) f(x) = (4x^2 – 4x + 13) /2 = 2x^2 - 2x + (13/2) = 2(x^2 – x) + (13/2) = 2(x^2 – x + 1/4) + 6 <--- 呢度開始唔明，請解釋 = 2(x - 1/2)^2 + 6 (b) & (c) 都唔明

回答 (1)

用戶7639

2011-06-19 9:12 pm

✔ 最佳答案

圖片參考：http://i56.tinypic.com/358qo3d.gif

http://i56.tinypic.com/358qo3d.gif

2011-06-19 19:27:53 補充：
2(x² – x) + (13/2)
=2[(x²-x+1/4)-1/4]+13/2
=2(x-1/2)²-2(1/4)+13/2
=2(x-1/2)²-1/2+13/2
=2(x-1/2)²+12/2
=2(x-1/2)²+6

2011-06-19 19:29:15 補充：
(b)2(x-1/2)²+6當(x-1/2)=0才可極小值。

👍 0 👎 0