更新1:
多謝你咁快答到先.. 請問你.有D英文/括號...後的 "2" 係咪2次方.?
中四MATHS QUAD.EQ.
2009-09-08 5:17 am
Solve 2abx^2 + acx - c^2 - 2bcx = 0 for x, where a, b, c are constants and a, b (are not equal to) 0
回答 (1)
2009-09-08 5:33 am
✔ 最佳答案
2abx2 + acx - c2 - 2bcx = 02abx2 + c(a - 2b)x - c2 = 0
Discriminant = c2(a - 2b)2 + 8abc2
= c2[(a - 2b)2 + 8ab]
= c2(a - 4ab + 4b2 + 8ab)
= c2(a + 4ab + 4b2)
= [c(a + 2b)]2
So roots of equation are [c(2b - a) + c(a + 2b)] / 4ab and [c(2b - a) - c(a + 2b)] / 4ab
Or 4bc / 4ab and -2ac / 4ab
Or c/a and -c/2b
2009-09-07 22:38:36 補充：
係
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