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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