What does f(5)=2 tell me about f(x)
You miss understand.
$f$ is a function, say $f$ is $f(x)$. For example consider $f(x)=x+3$, then $$f(5)=5+3=2$$ but $f$ is not identically $2$ because for example $f(0)=3$.
Now, $g(x)=2f(x)$, for what $x$ can you compute $g(x)$ ?
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Merlin's Beard
Updated on September 07, 2020Comments

Merlin's Beard about 3 years
As part of a math quiz I was given the following two functions:
f(5) = 2 and g(x) = 2 * f(x)
The way I interpret the first function is "return 2 regardless of the input" since the right hand side is just a constant. That would mean that f(x) will also result in 2, making the result of g(x) positive 4.
But I guess I'm missing something because that is not one of the available answers in the quiz.
Edit:
Apologies for the unclear question.
The full question in the quiz is as follows:
If $f(−5) = −2$ and $g(x) = −2 \cdot f(x)$, what point can you determine on the graph of $g$?
I realize now my interpretation was wrong. Like André said in the comment: I only know the output (2) of a given input (5). Knowing how to read the function f helped me solve the question, thanks guys.

Crostul about 9 yearsWhat is your question?

Paul Sundheim about 9 yearsYou were given the functions, but what question about the functions did they pose? It is true that $g(5)=4$ but that doesn't mean that $g(x)=4$.

André Nicolas about 9 yearsThe interpretation of the function $f$ is not right. All the equation says is "return $2$ on input $5$." It says nothing about what to return for other inputs.


Merlin's Beard about 9 yearsThanks for the nice explanation.

Asaf Karagila about 9 yearsI think the correct word is "misunderstand" and not "miss understand" (who is the daughter of Mr. and Mrs. Understand :P).