You are Here: Home >< Maths

# Official Edexcel C3 Discussion Thread watch

1. C3 retake tomorrow....
2. I'm scared to death.
3. I want an A*. I'm not gonna get one.
4. The last question in arseys answers is wrong when asked to find the range of fg(x) it is greater or equal to 3
5. (Original post by RamsFanNo1)
The last question in arseys answers is wrong when asked to find the range of fg(x) it is greater or equal to 3
oh for heavens sake not this again

it is NOT >= 3 it is just >3

I had to explain why several times, if you don't believe me look in the official mark scheme.

If you don't understand why, you don't understand functions fully.
6. (Original post by Arsey)
oh for heavens sake not this again

it is NOT >= 3 it is just >3

I had to explain why several times, if you don't believe me look in the official mark scheme.

If you don't understand why, you don't understand functions fully.
I fully understand functions, but anyways.. I've got a question. When the question asks me to find fg(x) or gf(x) and then it asks me its to find range/ domain what do i need to consider?

Help would be highly appreciated.
7. I think the easiest thing to do is to draw a flow chart and sketch the graphs

fg(x) works like this

input value x ----> function g ------> g(x) -------> function f ------> fg(x)

so your input value x has to belong to the domain of g

the range of g(x) (possible solutions / possible y coordinates) goes into function f but these solutions also have to belong to the domain of f. So only numbers which are BOTH in the range of g(x) and domain of f(x) will go into the second function f.

The possible answers are the range of fg(x)

Try substituting values into g and the solutions of that into f to see what is acceptable if you are unsure.

The key thing to remember that it isn't always as simple as to sketch the graph of the composite function and then look at the graph for the range of the composite function.

restrictions on the domains of the original function could have an impact.
8. (Original post by Arsey)
oh for heavens sake not this again

it is NOT >= 3 it is just >3

I had to explain why several times, if you don't believe me look in the official mark scheme.

If you don't understand why, you don't understand functions fully.
Sorry I just properly read the question and saw that the domain of g(x) > 1 - again I am very sorry!!
9. Oh god. This is going to be a tough cookie. I need to get an A*!

### Related university courses

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: June 14, 2010
The home of Results and Clearing

### 3,731

people online now

### 1,567,000

students helped last year
Today on TSR

Hang on, have Edexcel's come out already?

### University open days

1. SAE Institute
Animation, Audio, Film, Games, Music, Business, Web Further education
Thu, 16 Aug '18
2. Bournemouth University
Fri, 17 Aug '18
3. University of Bolton
Fri, 17 Aug '18
Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

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