I am doing a Maths qualification at the minute, and am stuck on a tutorial question that involves finding the natural domain of a function, and sketching a graph. Driving me up the wall, as I missed the lecture because of Croke Park hours (a great idea by the way, they really help teaching......). Anyone except OTB and Slimchance (neither of whom I would let walk my dog) think they could help??
Maths Help Needed
- Thread starter del boy
- Start date
On The Bridle
At the Start
I wouldn't let Grey walk your dog either.... He hasn't had it off with one YET...
On The Bridle
At the Start
By the way - you've more qualifications than the Quinn Groups accounts. Does this Maths one entitle you to an extra score on the dole or something?
On The Bridle
At the Start
No one is buying your Good Will Hunting act either by the way....you are watching the racing and doing your bollocks like the rest of us! How do you like them apples
No one is buying your Good Will Hunting act either by the way....you are watching the racing and doing your bollocks like the rest of us! How do you like them apples
My only saving grace is that I know when i hit rock bottom, you will be there to cushion the blow.
I wouldn't let Grey walk your dog either.... He hasn't had it off with one YET...
:lol:
S
SlimChance
Guest
Bar the Bull
At the Start
Sums are cool.
swedish chef
At the Start
The domain of a function is the set of numbers that you can plug into
the function and get out something that makes sense. This is also
called the set of numbers for which this function is defined. In this
case it is the set of all x, such that f(x) is a number.
One way to try to find the domain is to try a couple of numbers just
to get an idea of what might work.
(1) If we plug in 4, we get f(4) = (4+4)/(4^2 - 9) = 8/7.
(2) If we plug in 0, we get f(0) = (4+0)/(0^2 - 9) = 4/-9 = -(4/9)
(3) If we plug in 3, we get f(3) = (4+3)/(9-9) = 7/0 = Oops!
I'm sure you've been told in class that you can't divide by 0, so 7/0
is an answer that doesn't make sense, and one would say that f(x) is
not defined at x = 3. You would find that the same holds for x = -3.
Okay, so far we think that the domain of f(x) is all numbers except
3 and -3. But how do we know this is correct? In principle you would
have to try every real number other than these two to be sure. In
practice it is much easier. You just need to ask yourself a question:
Which is the only way this function can be undefined?
You know that you always get a fraction out of this function. (If you
get a whole number n, you can think of it as the fraction n/1.) The
only fractions that are undefined are those with 0 in their
denominators.
We have a zero in the denominator only when:
x^2 - 9 = 0
or only when
x = 3 or x = -3
This means that the function is undefined only at these two numbers,
so its domain is all real numbers but 3 and -3.
I hope that this has helped. :lol::lol:
granger
Senior Jockey
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Harbinger
At the Start
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- Mar 22, 2004
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- 11,282
What about complex numbers?
trudij
Senior Jockey
swedish chef
At the Start
On The Bridle
At the Start
I cannot believe a good decent slagging has descended into some kind of maths geek fest.....I am starting to question the validity of this forum...
S
SlimChance
Guest
I cannot believe a good decent slagging has descended into some kind of maths geek fest.....I am starting to question the validity of this forum...
The irony being that that the only equation del boy understands is where he blows up his tank.
swedish chef
At the Start
I haven't got a clue about any of this but I do know how to use google and the copy and paste function - that's my 'domain of a function' and it just takes some 'graph' to figure it out.
You wouldnt know when your full, never mind when you blow your load, so id keep out of it...
On The Bridle
At the Start
You could just about stretch to calculating the perms for a placepot the last time I met you so this domain of a function bullshit doesn't wash with me...:lol:
When you work out how much your into Nama for come back to me....