Shifting functions intro

An SAT Math micro-topic under Nonlinear functions (Advanced Math). Free to read — no account needed.

A shift moves a graph while keeping its shape the same.
Changing the input shifts it sideways, and changing the output shifts it up or down.
You can do one or both at once.
shift_intro.png
The figure shows a base curve with a horizontal shift and a vertical shift.
Changing the input, like f(x+2)f(x + 2), moves the graph sideways; adding a constant, like f(x)+3f(x) + 3, moves it up.
The shape stays exactly the same in both cases.
Adding inside the function moves it left, and subtracting inside moves it right — opposite to what the sign suggests.
Adding outside moves it up, and subtracting outside moves it down — just as the sign suggests.
So f(x−2)+5f(x - 2) + 5 is right 22 and up 55.
You can combine both shifts, and the vertex moves the same way as every point.
If the vertex was at (h,k)(h, k), then after shifting left 22 and down 33 it is at (h−2,k−3)(h - 2, k - 3).
Tracking the vertex describes the whole shift.

Worked examples

How does g(x)=f(x−1)+4g(x) = f(x - 1) + 4 shift the graph of f(x)f(x)?
The −1-1 inside moves it right 11 unit, and the +4+4 outside moves it up 44 units.
So gg is ff shifted right 11 and up 44.
shiftintro_ex1.png
A vertex is at (h,k)(h, k). Where is it after shifting 33 units down and 22 units left?
Left 22 subtracts 22 from xx, and down 33 subtracts 33 from yy.
So the new vertex is (h−2,k−3)(h - 2, k - 3).
shiftintro_ex2.png
Given g(x)=f(x−4)−1g(x) = f(x - 4) - 1, how is ff shifted to get gg?
The −4-4 inside moves it right 44 units, and the −1-1 outside moves it down 11 unit.
So gg is ff shifted right 44 and down 11.
shiftintro_ex3.png

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