Is there more to this problem? By saying f(4), you'd be inputting a 4 for every variable x. There is not enough info here to answer the question.
Answer:
USE GOOGLE BEFORE COMING HERE
Step-by-step explanation:
... <span>exactly one output for each input
This is an important concept; be certain that you understand it.
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The answer is 100 if that 5 and 2 is separate