one-to-one functions; inverse function. a function f is one-to-one if for each x in the domain of f...
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One-to-One Functions; Inverse Function
A function f is one-to-one if for each x in the domain of f there is exactly one y in the range and no y in the range is the image of more than one x in the domain.
A function is not one-to-one if two different elements in the domain correspond to the same element in the range.
x1
x2
x3
y1
y2
y3
x1
x3
y1
y2
y3
x1
x2
x3
y1
y3Domain
Domain
Domain
Range
Range
RangeOne-to-onefunction
Not a function
NOT One-to-onefunction
M: Mother Function is NOT one-one
Joe
Samantha
Anna
Ian
Chelsea
George
Laura
Julie
Hilary
Barbara
Sue
Humans Mothers
S: Social Security function IS one-one
Joe
Samantha
Anna
Ian
Chelsea
George
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333456789
433456789
533456789
633456789
Americans SSN
Is the function f below one – one?
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Theorem Horizontal Line Test
If horizontal lines intersect the graph of a function f in at most one point, then f is one-to-one.
Use the graph to determine whether the function f x x x( ) 2 5 12
is one-to-one.
Not one-to-one.
Use the graph to determine whether the function is one-to-one.
One-to-one.
The inverse of a one-one function is obtained by switching the role of x
and y
123456789
223456789
333456789
433456789
533456789
633456789
SSN
Joe
Samantha
Anna
Ian
Chelsea
George
Americans
The inverse of the social security function1S
Let and
Find
3)( xxf 31
)( xxg
))(())(( xfgandxgf
g is the inverse of f.
311 )( xxf
.Let f denote a one-to-one function y = f(x). The inverse of f, denoted by f -1 , is a function such that f -1(f( x )) = x for every x in the domain of f and f(f -1(x))=x for every x in the domain of f -1.
Domain of f Range of f
Range of f 1 Domain of f 1
f 1
f
Domain of Range of
Range of Domain of
f f
f f
1
1
Theorem
The graph of a function f and the graph of its inverse are symmetric with respect to the line y = x.
f 1
2 0 2 4 6
2
2
4
6 f
f 1
y = x
(2, 0)
(0, 2)
Finding the inverse of a 1-1 function
Step1: Write the equation in the form
Step2: Interchange x and y.
Step 3: Solve for y.
Step 4: Write for y.
)(xfy
)(1 xf
Find the inverse of
Step1:
Step2: Interchange x and y
Step 3: Solve for y
3
5
xy
3
5)(
xxf
3
5
yx
x
xxf
35)(1