問一題個經的題目了~感謝各位板大 - 經濟

although some of the statements below are true of both normal goods
and inferior goods, only one of the statement defines a normal good. which one?

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答案是：normal goods are those for which the income effect is negative.
詳解是 正常財之價格變動與需求量的變動關係，其中替代效果為負相關，所得效果亦為負相關。
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我的疑問：但是正常財若用x-y圖來畫，替代與所得效果不都是往右跑嗎?
那麼這種題目，到底要用哪種解好呢?


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