1題f.4函數 望解答

2009-12-25 6:59 pm
f(x)=x^2+(k+1)x+k,若f(k)+f(-k)=4 , 求k

回答 (1)

2009-12-25 7:18 pm
✔ 最佳答案
f(k) = k^2 + (k+1)k + k ;
f(-k) = (-k)^2 + (k+1)(-k) + k = k^2 - k^2 - k + k = 0 ;
f(k) + f(-k) = 4
f(k) + 0 = 4
k^2 + (k+1)k + k = 4
k^2 + k^2 + k + k = 4
k^2 + k - 2 = 0
(k - 1)(k + 2) = 0
k = 1 or k = - 2


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