1.f(x)=x^2-kx
(a) if f(x+2)-f(x-2kx-32 ,求k ans:8
functions --help
2007-01-18 5:22 am
回答 (2)
2007-01-18 6:43 am
✔ 最佳答案
f(x) = x^2 - kxso,
f(x+2) - f(x-2)= kx - 32
[ (x+2)^2 - k(x+2) ] - [ (x-2)^2 - k(x-2) ] = kx - 32
8x - 4k = kx - 32
as the equation satisfies for all x, so 8x corresponds to kx and -4k correspond to -32
k must be 8.
但我不明白第2條問題，不能解答。
參考: 物理本科生
2007-01-20 4:03 am
1a)f(x+2)-f(x-2)
=[(x+2)^2-k(x+2)]-[(x-2)^2-k(x-2)]
=(x^2+4x+4 -kx -2k) -(x^2-4x+4-kx+2k)
=8x-4k
comparing the coefficient:
k=8
2)是的,因為當我地completing square的時候,
y =a(x-h)+q
↑是max./min.的對應軸
因此座標y的數字就係max./min.的vaule
=[(x+2)^2-k(x+2)]-[(x-2)^2-k(x-2)]
=(x^2+4x+4 -kx -2k) -(x^2-4x+4-kx+2k)
=8x-4k
comparing the coefficient:
k=8
2)是的,因為當我地completing square的時候,
y =a(x-h)+q
↑是max./min.的對應軸
因此座標y的數字就係max./min.的vaule
收錄日期: 2021-04-12 22:42:25
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20070117000051KK04503