Saturday, 17 December 2016

algebra precalculus - What makes a function not defined?



I have started studying precalculus and would then start up with calculus. While studying about functions I wondered whether this function would be defined at a or not. Take a look at it. f(x)=(xa)(xb)(xc)...(xn)(xa)




Here if we will simplify it further then the term (xa) would cancel out making the function defined at a but if we would leave it as such it would be undefined at that point.



I asked this question because I found in some sources that the graph of such functions have an open dot at that point indicating it discontinuous at that point. But I couldn't explain it. Are the expressions before and after cancelling different or it's something else?



I would be highly obliged for your help and thanks ...


Answer



Consider the following functions: f(x)=5



g(x)=5(x2)(x2)




The function g is not defined at x=2, but agrees with f at every other point.



So we would say these functions are not the same, because their domains are different.


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