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# Quick function graphs question Watch

1. Say we have the function f(x)=x^2

Then the graph is translated in the positive x-direction by +1.

Why do we write f(x-1) to describe the translation? Because if all the x values moved by one, say x was originally 2, so f(x) = 4, but now if you put in x= 2 you then have f(1) = 1. Shouldn't it be f(x+1), since the graph has been moved to the right by one?

I'm a bit confused....
2. (Original post by ThatPerson)
Say we have the function f(x)=x^2

Then the graph is translated in the positive x-direction by +1.

Why do we write f(x-1) to describe the translation? Because if all the x values moved by one, say x was originally 2, so f(x) = 4, but now if you put in x= 2 you then have f(1) = 1. Shouldn't it be f(x+1), since the graph has been moved to the right by one?

I'm a bit confused....
If you draw the graph out, the new graph then has f(2-1)=1. i.e. on the new graph, where x=2, we have y = 1. Which is correct?
3. (Original post by 2710)
If you draw the graph out, the new graph then has f(2-1)=1. i.e. on the new graph, where x=2, we have y = 1. Which is correct?
Oh thanks!

So it is because the y values will also change on the graph, so the x value has to be subtracted, because x=2 is now what was x=1 on the previous graph.
4. (Original post by ThatPerson)
Oh thanks!

So it is because the y values will also change on the graph, so the x value has to be subtracted, because x=2 is now what was x=1 on the previous graph.
As a rule of thumb you write the opposite of what you're doing. So for if it it translated in the positive x axis then .
For a in the negative x direction
For y it is for the negative y direction and in the positive y direction.

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