Friday, 26 September 2014

elementary set theory - Functions and unions on sets

I seek an elementary set theory proof. (All new to me.)



Let f:XY be a function. Ai are subsets of X, Bi are subsets of Y.



Prove that f(iAi)=if(Ai)



I sense that the approach is to show they're subsets of each other, but I can't out how to formulate this.




(Whilst we're at it, is the same true with the intersection?)

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