f(2) = 3(2) - 5 = 6 - 5 = 1

f(3) = 3(3) - 5 = 9 - 5 = 4

f(2) = 3(2) - 5 = 6 - 5 = 1

f(3) = 3(3) - 5 = 9 - 5 = 4

What you need to understand about functions is you are plotting x versus f(x). For every particular value of x there is a single corresponding f(x); f(x) = 3x - 5 tells you how the functions defined for values of x. You only need to put in values for x and solve for f(x). You could even plot x against f(x) by substituting values for clear understanding.

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