SOLUTION: Which of the following are functions? a. f(x) = x + 4 b. f(x) = 3 if x>2 otherwise f(x) = -2 c. f(x) = 7 if x>0 or f(x) = -7 if x<0 or f(x) = 7 or -7 if x = 0 I belie

Algebra ->  Functions -> SOLUTION: Which of the following are functions? a. f(x) = x + 4 b. f(x) = 3 if x>2 otherwise f(x) = -2 c. f(x) = 7 if x>0 or f(x) = -7 if x<0 or f(x) = 7 or -7 if x = 0 I belie      Log On


   

Question 235802: Which of the following are functions?
a. f(x) = x + 4
b. f(x) = 3 if x>2 otherwise f(x) = -2
c. f(x) = 7 if x>0 or f(x) = -7 if x<0 or f(x) = 7 or -7 if x = 0
I believe A is a function but that B and C are not, but I am not sure. How do I tell?
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
A and B are both functions since they pass the vertical line test (plot them out to verify). However, C is not a function since if x=0, then f(x)=7 or -7. Remember, a relation is a function only if each input has exactly one output. Since the input of x=0 produces two outputs, this means C is not a function.