How do I write the equation of a given graph?

Question

Not in y = mx+b form but in like a f(x) = kinda form

Answer 1

Not really sure I understand your question, but f(x) and y are basically interchangeable, though y can be used for any graph and f(x) is used for a function.

y = 2x + 3 is the same as f(x) = 2x + 3, for example.