Advanced functions

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When one function is built from another by shifts, like g(x)=f(x−2)+2g(x) = f(x - 2) + 2, the graph of gg is just the graph of ff moved.
A change inside the function shifts it horizontally, and a change outside shifts it vertically.
advfn_shift.png
Read the two shifts separately.
In g(x)=f(x−2)+2g(x) = f(x - 2) + 2, the (x−2)(x - 2) moves the graph right by 22, and the +2+2 moves it up by 22.
So if the graph of ff has its vertex at (1,0)(1, 0), the graph of gg has its vertex at (1+2, 0+2)=(3,2)(1 + 2,\ 0 + 2) = (3, 2); every point of ff moves the same way.
To go the other way and recover ff from gg, undo the shifts.
Since gg is ff moved right 22 and up 22, the graph of ff is the graph of gg moved left 22 and down 22.
So a vertex of gg at (3,2)(3, 2) came from a vertex of ff at (1,0)(1, 0).
You can also read a single value of ff straight from the graph of gg.
Because g(x)=f(x−2)+2g(x) = f(x - 2) + 2, putting x=3x = 3 gives g(3)=f(1)+2g(3) = f(1) + 2, so f(1)=g(3)−2f(1) = g(3) - 2.
Read g(3)g(3) off the graph and subtract 22: match the input, then adjust for the outside shift.

Worked examples

The graph of gg is shown, where g(x)=f(x+3)−1g(x) = f(x + 3) - 1.
advfn_qa.png
What is the vertex of the graph of ff?
The (x+3)(x + 3) moves ff left 33 and the −1-1 moves it down 11, so ff is recovered by moving gg right 33 and up 11.
The vertex of gg is (−2,2)(-2, 2), so the vertex of ff is (−2+3, 2+1)=(1,3)(-2 + 3,\ 2 + 1) = (1, 3).
The graph of gg is shown, where g(x)=f(x+1)−3g(x) = f(x + 1) - 3.
advfn_qb.png
The graph of ff is a parabola; what is its vertex?
The (x+1)(x + 1) moves ff left 11 and the −3-3 moves it down 33, so ff is gg moved right 11 and up 33.
The vertex of gg is (2,−2)(2, -2), so the vertex of ff is (2+1, −2+3)=(3,1)(2 + 1,\ -2 + 3) = (3, 1).
The graph of gg is shown, where g(x)=f(x−3)+1g(x) = f(x - 3) + 1.
advfn_qc.png
What is the value of f(1)f(1)?
Since g(x)=f(x−3)+1g(x) = f(x - 3) + 1, set x−3=1x - 3 = 1, so x=4x = 4; then g(4)=f(1)+1g(4) = f(1) + 1, which gives f(1)=g(4)−1f(1) = g(4) - 1.
From the graph g(4)=4g(4) = 4, so f(1)=4−1=3f(1) = 4 - 1 = 3.

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