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【A-Level數(shù)學 Integration by parts】

Integration by parts：

Use Integration by parts to find ∫xsin3x dx ；

Using your answer to part 1,find ∫x^2cos3x dx。

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昨日 [ 每日一題 ] 答案

With reference to the relevant type of elasticity of demand, explain the terms (I) inferior good, and (ii) complementary good.

題目分析：

該題考察了YED和XED的取值問題。答題結(jié)構(gòu)：

①首先給出ED（需求彈性）的概念：Elasticity of demand concerns the responsiveness of demand to a change in a variable.

②然后使用YED和XED分別討論兩種商品的性質(zhì)：An inferior good is one that is bought in smaller quantities as income rises, as it is replaced by a superior good.

It involves income elasticity which has a negative value.

An example might be motor cycles replaced by cars.

Complementary goods are ones that are jointly demanded, such as coffee and cream.

Cross price elasticity of demand is relevant and is negative as the rise in price of one good reduces the quantity demanded of a complement.