Question 183673
f(x) = 2x + 9
Step 1: for convenience, let's replace f(x) with y
y=2x+9
Step 2: replace all y's with x and replace all x's with y
x=2y+9
Step 3: express x in terms of y
...
x=2y+9
2y+9=x
2y=x-9
y=(x-9)/2

Step 4: replace y with f<sup>-1</sup>(x)

f<sup>-1</sup>(x)=(x-9)/2

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