# Geometry Help (Basic Explanations PLZ)

• Apr 20th 2009, 07:49 AM
Papercut619
Geometry Help (Basic Explanations PLZ)
Hi there people. my first time posting.. and this really is my last resort.Maths teacher at school thinks we know everything.. leaving out basic explanations of words..

Help would be greatly apreciated as soon as possible..work due next day.. Ive got so many questions ill rather as for 1 thing and get some marks.. YAY..

Anyway
Please could someone explain what Domain and Range is.. Very basic plz!

Then could you answer what Domain and Ranges are in these four examples..

1.f(x)=(x+1)squared -4 its all functions.. Thanks allot if you can help
2.g(x)=-(x+1) "" -2
3.h(x)=-(x-1) "" +4
4.j(x)=(x-4) "" -2
4.

I really sturggle in my Maths.. Failed this term 24% (Crying)
• Apr 20th 2009, 08:14 AM
running-gag
Hi

The domain is the set of x for which you can compute f(x)
The range is the set of y such that you can find at least one x for which f(x)=y

f(x)=(x+1)²-4
You can compute f(x) for all x real therefore domain is $\displaystyle \mathbb{R}$

For every x real $\displaystyle (x+1)^2 \geq 0$ therefore $\displaystyle (x+1)^2 -4 \geq -4$. f(x) can take any value greater than -4.
Range is $\displaystyle [-4 , +\infty($
• Apr 20th 2009, 09:30 AM
Papercut619
Forever greatful man
Just what i asked for :)