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Inverse of One-To-One Function Password GJVT

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INVERSE OF

ONE-TO-ONE
FUNCTION
Original Function
x -4 -3 -2 -1 0 1 2 3 4
y -9 -7 -5 -3 -1 1 3 5 7

Inverse Function
x -9 -7 -5 -3 -1 1 3 5 7
y -4 -3 -2 -1 0 1 2 3 4
Example

Find the inverse of the function


describe by the set of ordered pairs.
{(1,-3), (2,1), (3,3), (4,5,), (5,7}

Solution
{(-3,1), (1,2), (3,3), (5,4,), (7,5}
Example

Find the inverse of the function


𝒇 𝒙 = 𝟑𝒙 + 𝟏
To find the inverse of one-to-one function

A. Write the function in the form of


𝑦=𝑓 𝑥 .
B. Interchange the 𝑥 and 𝑦 variables.
C. Solve for 𝑦 in terms of 𝑥
Example Find the inverse of the function 𝒇 𝒙 = 𝟑𝒙 + 𝟏

A. Write the function in the form of 𝑦 = 𝑓 𝑥 .

𝒇 𝒙 = 𝟑𝒙 + 𝟏
𝒚 = 𝟑𝒙 + 𝟏
Example Find the inverse of the function 𝒇 𝒙 = 𝟑𝒙 + 𝟏

B. Interchange the 𝑥 and 𝑦 variables.

𝒚 = 𝟑𝒙 + 𝟏
𝒙 = 𝟑𝒚 + 𝟏
Example Find the inverse of the function 𝒇 𝒙 = 𝟑𝒙 + 𝟏

C. Solve for 𝑦 in terms of 𝑥


𝒙 = 𝟑𝒚 + 𝟏
−𝟑𝒚 + 𝒙 = 𝟏
−𝟑𝒚 = −𝒙 + 𝟏 𝒙−𝟏
𝒚=
−𝟑𝒚 −𝒙 + 𝟏 𝟑
=
−𝟑 −𝟑
−𝒙 + 𝟏 Since the inverse of the
𝒚= function is denoted by 𝒇−𝟏,
−𝟑
−(𝒙 − 𝟏) 𝒙−𝟏
𝒚= 𝑓 −1
(𝑥) =
−𝟑 𝟑
EXAMPLE 2: Find the inverse of 𝒈 𝒙 = 𝒙 − 𝟐 𝟑

A. Write the function in the form of 𝑦 = 𝑓 𝑥 .

𝟑
𝒈 𝒙 = −𝟐 𝒙
𝟑
𝒚=𝒙 −𝟐
EXAMPLE 2: Find the inverse of 𝒈 𝒙 = 𝒙 − 𝟐
𝟑

B. Interchange the 𝑥 and 𝑦 variables.


𝟑
𝒚=𝒙 −𝟐
𝟑
𝒙=𝒚 −𝟐
EXAMPLE 2: Find the inverse of 𝒈 𝒙 = 𝒙 − 𝟐 𝟑

C. Solve for 𝑦 in terms of 𝑥


𝒙= −𝟐 𝒚 𝟑
𝒚𝟑 = 𝒙 + 𝟐
𝟑
−𝒚 + 𝒙 = −𝟐 𝟑 𝟑
𝟑
𝒚 = 𝒙+𝟐
𝟑
−𝒚 = −𝟐 − 𝒙
𝟑
−𝒚 𝟑 −𝒙 − 𝟐 𝒚= 𝒙+𝟐
= Since the inverse of the
−𝟏 −𝟏 function is denoted by 𝒇−𝟏,
−𝒚 𝟑 −(𝒙 + 𝟐)
= −𝟏
𝒈 (𝒙) =
𝟑
𝒙+𝟐
−𝟏 −𝟏
𝟐𝒙+𝟏
EXAMPLE 3: Find the inverse of 𝒇 𝒙 =
𝟑𝒙−𝟒

A. Write the function in the form of 𝑦 = 𝑓 𝑥 .


𝟐𝒙 + 𝟏
𝒇 𝒙 =
𝟑𝒙 − 𝟒
𝟐𝒙 + 𝟏
𝒚=
𝟑𝒙 − 𝟒
𝟐𝒙+𝟏
EXAMPLE 3: Find the inverse of 𝒇 𝒙 =
𝟑𝒙−𝟒

B. Interchange the 𝑥 and 𝑦 variables.


𝟐𝒙 + 𝟏
𝒚=
𝟑𝒙 − 𝟒
𝟐𝒚 + 𝟏
𝒙=
𝟑𝒚 − 𝟒
𝟐𝒙+𝟏
EXAMPLE 3: Find the inverse of 𝒇 𝒙 =
𝟑𝒙−𝟒

C. Solve for 𝑦 in terms of 𝑥


𝟐𝒚 + 𝟏 𝒚(𝒙 − 𝟐) 𝟒𝒙 + 𝟏
𝒙= =
𝟑𝒚 − 𝟒 𝒙−𝟐 𝒙−𝟐
𝒙 𝟑𝒚 − 𝟒 = 𝟐𝒚 + 𝟏 𝟒𝒙 + 𝟏
𝒚=
𝒙−𝟐
𝟑𝒙𝒚 − 𝟒𝒙 = 𝟐𝒚 + 𝟏
𝟑𝒙𝒚 = 𝟐𝒚 + 𝟒𝒙 + 𝟏 𝟒𝒙 + 𝟏
𝒇−𝟏 (𝒙) =
𝟑𝒙𝒚 − 𝟐𝒚 = 𝟒𝒙 + 𝟏 𝒙−𝟐
𝒚(𝒙 − 𝟐) = 𝟒𝒙 + 𝟏
EXAMPLE 4: Find the inverse of 𝒇 𝒙 = 𝒙𝟐 + 𝟒𝒙 − 𝟐

It is not a one-to-
one function
EXAMPLE 4: Find the inverse of 𝒇 𝒙 = |𝒙|

It is not a one-to-
one function
PRACTICE EXERCISE

Find the inverse of the given function.

1.𝑓 𝑥 = 3𝑥 − 8
2
2.𝑔 𝑥 = 𝑥 − 6𝑥 − 7
4𝑥+2
3.ℎ 𝑥 = 𝑥−3

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