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GRE 8767 #20

Posted: Sat Oct 18, 2014 2:56 pm
by d555
Suppose that f(x+1)=f(x) for all real x. If f is a polynomial and f(5) = 11, the f(15/2) is:

a)-11
b) 0
c)11
d) 33/2
e)not uniquely determined by the information given

I thought answer e) but actually it's c), I don't figure out why?

Re: GRE 8767 #20

Posted: Sun Oct 19, 2014 12:11 am
by mathblob23481
The key is to realize that f is a polynomial and use the fact that f(5) = 11 with f(x) = f(x+1) for all real x to deduce it must be constant. Hence, you can obtain f(7.5).