You are Here: Home >< Maths

# Another C3 functions question Watch

1. The function f is defined by f : x → 3 + ln (x + 2), x ∈ R , x ≥ k, where k is a constant. Given that the range of f is f(x) ≥ 3,

a) find the value of k,

b) find f −1(x), stating its domain clearly.

Can someone tell me if I have answered this question correctly?

For part a), I drew a graph of the function and worked out that when y=3, x=-1, therefore the domain must be x ≥ -1, therefore k = -1.

For part b) I worked out that the inverse function is ex-3 -2 which I am not sure is correct.
I don't know how to find the domain for this though... How do you do it?
2. (Original post by jessyjellytot14)
...
Domain of the inverse is the range of the original. Remember what happens with y and x when it comes to the inverse, apply the same idea to the constraints.

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: August 26, 2016
Today on TSR

### What is the latest you've left an assignment

And actually passed?

### Simply having a wonderful Christmas time...

Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• Poll
Useful resources

### Maths Forum posting guidelines

Not sure where to post? Read the updated guidelines here

### How to use LaTex

Writing equations the easy way

### Study habits of A* students

Top tips from students who have already aced their exams

## Groups associated with this forum:

View associated groups
Discussions on TSR

• Latest
• ## See more of what you like on The Student Room

You can personalise what you see on TSR. Tell us a little about yourself to get started.

• The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.