[請益] 數經
請問如何證 dx1/dp and dx2/dp 不會同時小於0呢
p為價格 y產出 x1, x2為要素
(嚴格來說,符號是不是d,應該是partial 偏微的符號,但我打不出來)
-f1f22+f2f12
dx1/dp= ----------------
p(f11f22-f12^2)
-f2f11+f1f12
dx2/dp= ---------------
p(f11f22-f12^2)
要證明以上2個式子不會同時為負
好像是用反證法
利用 dy/dp>0 p上升 →y上升 y=f(x1,x2)
不過再來我就沒頭緒了 請高手指點^^
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