
(2)已知+f(2x+1)=3x^3-2x^2+1,求f(x)
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解:f(2X+1)=3X³-2X²+1
设t=2X+1,则X=(t-1)/2
f(t)=3×[(t-1)/2]³-2×[(t-1)/2]²+1
=3/8(t³-3t²+3t-1)-1/2(t²-2t+1)+1
=3/8t³-13/8t²+17/8t+1/8
所以f(X)=3/8X³-13/8X²+17/8X+1/8
设t=2X+1,则X=(t-1)/2
f(t)=3×[(t-1)/2]³-2×[(t-1)/2]²+1
=3/8(t³-3t²+3t-1)-1/2(t²-2t+1)+1
=3/8t³-13/8t²+17/8t+1/8
所以f(X)=3/8X³-13/8X²+17/8X+1/8
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