g(x)=x^(1/3)
prove g is surjective
答案:
let x=y^3
g(x)=y
g is surjective
我不明白為何這樣就可證明g is surjective
surjective function-10分
2008-03-19 3:42 am
回答 (3)
2008-03-19 9:20 am
✔ 最佳答案
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Definition of Surjective:
圖片參考：http://hk.geocities.com/tate_poon/knowledge/20080319_2.gif
Let y be a testing element belonging to B.
Let x=y3, where x should be an element of A.
As g(y3)=y, there exists an element of A such that g(x)=y.
As y is arbitrary testing element, every y can draw the above conclusion.
This satisfies the definition of surjective.
2011-08-26 5:52 am
sin(x)=y
let sin^-1y=x
sin(sin^(-1)y)=y
also,but obviously,sin(x) is not surjective,
how to explain this?
2011-08-25 21:52:47 補充：
Also ,how to use the existence of inverse?
let sin^-1y=x
sin(sin^(-1)y)=y
also,but obviously,sin(x) is not surjective,
how to explain this?
2011-08-25 21:52:47 補充：
Also ,how to use the existence of inverse?
2008-03-19 8:30 am
就這一條，我們可以用existence of inverse => bijective => surjective，會方便好多。
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