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# C3 - Functions grrrr. watch

1. I'm not a happy bunny. I've just found all the work set for us this summer on C3 and functions. I've re-read my notes/the textbook and i'm still confused.. Didn't help as i didn't properly understand it make in july but hey ho.

Right here goes.
Find the range of
a) f(x)=4(x-2) (xER, x greater than/equal to 0)
b) g(x)=x^3 +1 (xER)

For a) i think i've done it and the answer i got was y > 4
(i drew a graph of it)

For b) i've drawn a basic sketch graph of it but i really have no idea how to find the range now...

Could someone put me on the right track or something please?

Thanks.

Ohh and i've looked at the useful links on here, but is there a website which is good for C3 stuff? By the way i'm doing Edexcel?
2. (Original post by boy)
a) You could just substitute x=0 in the equation and get 4 since . So it's y>4, you're right
Oooh ok. Trust me to do it the long way, i'm such a dim wit.

(Original post by boy)
b) It's a cubic equation so what is the lowest and highest turning point on the graph?
O ok. I have to work that out.. Ok i'll go and look that up!
3. (Original post by boy)
a) You could just substitute x=0 in the equation and get 4 since . So it's y>4, you're right

b) It's a cubic equation so what is the lowest and highest turning point on the graph?
erm, I don't think a) is right, if x = 0, (x-2) = -2, => f(x) = -8.... => f(x) >= -8

b) it's a cubic, therefore it must start in 1 corner, and finish in the other, and so it spans the whole page, so the range is?
4. (Original post by JoMo1)
erm, I don't think a) is right, if x = 0, (x-2) = -2, => f(x) = -8.... => f(x) >= -8

b) it's a cubic, therefore it must start in 1 corner, and finish in the other, and so it spans the whole page, so the range is?
My mistake. You're right
5. I think you drew the graph wrong which is what threw you off course.

a) When x=0, y = 4(0-2) = -8. Plug in the numbers for x=1, 2, 3... and you'll see that it's a straight line that starts at y = -8 and goes up through the x-axis

So the range is y is greater than or equal to -8 and y still belongs to the reals

b) The range would just be y belongs to the reals. You could make y infinitely big or small depending what x value you stick in.

The graph looks like this just shifted up by 1:

Best website I used was www.mathsnet.net, lots of worked examples which make it easy for those that didn't pay attention to anything said in class - like myself!
6. Just a small thing, for the range you may lose marks if you write so you should write or what ever you find the correct answer to be.
7. That website's no longer free - what prat decided to make money out of it!?!

In that case stick to the books!
8. I left out this complete topic and I still got an A. Much like i didnt bother learning vectors. Leave it out
9. ^I think it's better for her to do it
10. (Original post by neon)
I left out this complete topic and I still got an A. Much like i didnt bother learning vectors. Leave it out
May not be the best idea for her learning.
11. (Original post by neon)
I left out this complete topic and I still got an A. Much like i didnt bother learning vectors. Leave it out
hmmm if it was an exam paper i would usually!!

but i've got sheets of this stuff to do!

ok thanks for your help everyone.
i think i get the range for a) but b)'s still puzzling me. Oh i do hate maths to confusing perhaps i'll come back to it later.

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