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標題:

f(x)=x2-kx, f(x+2)-f(x-2)=kx-32 求k

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發問:

f(x)=x2-kx, f(x+2)-f(x-2)=kx-32 求k

最佳解答:

f(x+2)-f(x-2)=kx-32 (x+2)^2-k(x+2)-(x-2)^2+k(x-2)=kx-32 (x+2+x-2)(x+2-x+2)-kx-2k+kx-2k=kx-32 8x-4k=kx-32 8x=kx k=8

其他解答:

f(X) = x2-kx, f(x+2)= (x+2) 2 - k ( x+2) f(x-2)= (x-2) 2 - k (x-2) i.e. (x+2) 2 - k ( x+2) - [(x-2) 2 - k (x-2)] = kx-32 --> 2x +4 - kx -2k - [2x - 4 - kx +2k] = kx-32 --> 2x + 4 -kx -2k -2x +4 + kx -2k = kx-32 --> 8 - 4k = kx-32 --> 8 + 32 = kx + 4k --> 40/ (x + 4) = K