Posted by Samantha Joseph on Tuesday, November 30, 2010 at 8:58am.
5. Which of the following are functions?
The last two problems, i.e., b & c, are multi part relations consider all parts when determining whether or not these relations are functions. Explain your reasoning for a, b, and c.
a. f(x) = x + 3
b. f(x) = 73 if x>2 otherwise f(x) = 1
c. f(x) = 79if x>0 or f(x) = 9 if x<0 or f(x) = 9 or 9 if x = 0

Mat101  MathMate, Tuesday, November 30, 2010 at 9:09am
To determine if a relation is a function, ask one very important question:
does the relation satisfy the onetoone condition? That is to say does the relation maps to two values in the codomain (range) from one value in the domain?
Examples:
f(x)=sqrt(x) is not a function because sqrt(x) results in two values.
f(x)=any polynomial with real (i.e. not complex) coefficients is a function, because polynomials satisfy the onotoone requirement.
Now can you pick out the functions from the above list, and state why the other(s) is not?
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