Price Theory by Landsburg 的租稅歸宿 - 經濟

小弟雖然已修完個、總體外加財政學,但一直沒有數學的底子（汗）

最近重翻Landsburg的Price theory想把書末的Calculus Supplement題目做完

從最基礎打起,結果在Chapter1 馬上就卡題！希望版上善良、聰明的板友們可以指點一下

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Let S(P) and D(P) be the supply and demand functions for apples. Suppose that

an excise tax of T is imposed and the posttax equilibrium price for apples is

P. Treating P as a function of T, (1) use the equation:

D(P) = S(P-T) --------"1"

and the chain rule to derive a formula for the derivative dP/dT.

(2) Let Ps be the price that sllers actually receive. Use the result of

problem 1 and the equation :

Ps = P - T --------"2"

to derive and simplify a formula for the derivative dPs/dT.
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在此提供第一題解答：

dP/dT = S'(P-T) / ( S'(P-T) - D'(P) )


其實我直接把"2"代換入"1"做全微分出來的答案好像也沒有錯,但這樣真的妥當嗎？
哪位好心的版友可以告訴我如何使用dP/dT求出正解？如果可以順便附上算式過程

感恩！






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