教我a..我唔明a..maths..

2008-03-12 4:57 am
因AB的斜率 = AP的斜率 + BP的斜率

-3 / 4 = - (k + 2) / 2 + (k - 4) / 6

-3(3) = -6(k + 2) + 2(k - 4) <<<其實我最唔明ge係,點解-3/4會轉左-3(3)ge??

-9 = -6k – 12 + 2k – 6

k = -9 / 4
更新1:

不過我ge書答案係k=-11/4 ...我係想問ge係-3/4會轉左-3(3)????????

回答 (2)

2008-03-12 5:29 am
✔ 最佳答案
因為第二部其實做了以下的計算

(-3 /4) * 6 * 2 = [-(k+2) /2 + ( k - 4) /6 ] * 6 * 2
(-3/4) * 12 = -6(k+2) + 2(k-4)

所以才有
-3(3) = -6(k+2) + 2(k-4)

2008-03-11 21:34:24 補充:
還有,你第三部計錯了,應該是

-9 = -6k -12 + 2k - 8
4k = -11
k = -11/4

2008-03-12 02:07:31 補充:
左手邊係
(-3)*(12)/(4)
約簡後
(-3)(3)

你明白了嗎?
2008-03-12 5:23 am
你點計出個-9/4嫁,根本由第二行開始已經係錯嫁喇,我計既答案係-1/4= =


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