摘要:8.已知f(3x)=4xlog23+233.则f+-+f(28)的值等于 . [解析] 令3x=t.∴x=log3t.∴f(t)=4log23·log3t+233. 即f(t)=4log2t+233. ∴f+-+f(28) =4(log22+log24+log28+-+log228)+8×233 =4·log22·22·23-28+8×233 =4·log2236+1864 =4×36+1864=2008. [答案] 2008
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