eli5: Why does y=f(x+2) move it two units to the left (not right)?

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This is also the case where y=f(2x) where it dilates by a factor of 1/2. Why are they seemingly the opposite of what intuition tells me?

Edit:
Thanks guys 🙂 got it.

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5 Answers

Anonymous 0 Comments

Because you’re thinking too directly. The important idea is what change in x is necessary to give the same output.

Consider f(x) when x = 0, then the outcome is f(0)

For f(x+2), x has to be -2 for the outcome to be f(0). If x = 2, then f(x+2) = f(4) not f(0).

Should it move left or right?

The same reasoning for stretching and shrinking. Consider f(x) when x = 2 which gives f(2). For f(2x) what does x have to be to get f(2)? Does x have to be 1/2 or 4?

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