You are Here: Home >< Maths

# C3 intro Watch

1. I'm really struggling with fractions does anyone have any tips on how to solve this question:
2. No question showing up for me...
3. Hang on let me type it out looks like it didn't work first time round ☺️
4. So, f(x)= 1- 3/(x+2) + 3/(x+2)^2 where x\= -2

Show that f(x) = (x^2+x+1)/ (x+2)^2
5. Then part b) and c) is also a bit hazy for me too

B) Show that x^2+ x+1>O for all values of x

C) show that f(x) >O for all values of x.
6. (Original post by Trudy9)
So, f(x)= 1- 3/(x+2) + 3/(x+2)^2 where x\= -2

Show that f(x) = (x^2+x+1)/ (x+2)^2
You want to make the denominators the same. The highest denominator you have is (X+2)^2, so you need to multiply 1 by (x+2)^2 and then multiply -3 by (x+2) and then keep the last bit as it is...
7. (Original post by Trudy9)
x
Remember that to add fractions, they must have the same denominator, so you can cross multiply as necessary to make sure that they have the same denominator.

Eg (1/2) + (1/3) is given a common denominator 6 by 'multiplying' the first by 3 and the second by 2 to give (3/6) + (2/6) = (5/6). Yours already has the common factor of (x+2) so it is not as confusing, but you apply similar logic.
8. (Original post by Trudy9)
Then part b) and c) is also a bit hazy for me too

B) Show that x^2+ x+1>O for all values of x

C) show that f(x) >O for all values of x.
part b is showing that f(x) is an increasing function, so you need to differentiate the function and show that it is always positive !
9. (Original post by fefssdf)
part b is showing that f(x) is an increasing function, so you need to differentiate the function and show that it is always positive !
No it isn't - it's showing that the function is > 0 for all x. That's completely different from showing that a function is increasing! There's no differentiation required in this question
10. (Original post by Trudy9)
B) Show that x^2+ x+1>O for all values of x
Think about completing the square. What can you say about (number)^2 + (positive number)? Is that always positive, is it always negative is it what...?

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 27, 2016
Today on TSR

### Last-minute PS help

100s of personal statements examples here

### Loneliness at uni

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.