Analysis and Approaches for IBDP Maths Ebook 2 | Page 23

4
Paper 2 Section A – Restricted Domains for
1
Example
The function f is defined as
f x
� � � , x �� 10. The domain of f is restricted
2
( ) x 4 5
such that
1
f �
exists.
(a) State the largest possible domain of f .
(b)
(c)
Find the expression of
State the domain of
1
f � .
1
f � .
[2]
[3]
[1]
Solution
(a) { x: x� 2}
A2
(b)
f x
2
( ) ( x 4) 5
y�
x
� � � (A1) for correct function
2
� 9
2
� � � (M1) for swapping variables
x
y
x�9
� y
2
y� x�
9
9
�
� f 1 ( x) � x � 9
A1
(c) { x: x�� 5}
A1
[2]
[3]
[1]
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