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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Mathematical Methods CAS => Topic started by: kurrymuncher on November 06, 2008, 07:36:38 pm

Title: addition- multiplication of ordinates
Post by: kurrymuncher on November 06, 2008, 07:36:38 pm: hey just came across a question in tssm 07 or 08, cant remember. But it had 2 graphs without any equations given and asked you to sketch
f(x) *g(x). How do you do that? i multiplied each y coordiante but it was still wrong.

Its very last minute, sorry :)
Title: Re: addition- multiplication of ordinates
Post by: BiG DaN on November 06, 2008, 07:38:07 pm: Quote from: kurrymuncher on November 06, 2008, 07:36:38 pm
hey just came across a question in tssm 07 or 08, cant remember. But it had 2 graphs without any equations given and asked you to sketch
f(x) *g(x). How do you do that? i multiplied each y coordiante but it was still wrong.

Its very last minute, sorry :)

i just did this exam
u just multiply the y co-ordinates
make sure to use the negatives aswell tho
Title: Re: addition- multiplication of ordinates
Post by: danieltennis on November 06, 2008, 07:38:24 pm: Quote from: kurrymuncher on November 06, 2008, 07:36:38 pm
hey just came across a question in tssm 07 or 08, cant remember. But it had 2 graphs without any equations given and asked you to sketch
f(x) *g(x). How do you do that? i multiplied each y coordiante but it was still wrong.

Its very last minute, sorry :)

Which exam and what question?
Title: Re: addition- multiplication of ordinates
Post by: Lulu on November 06, 2008, 07:38:36 pm: http://vcenotes.com/forum/index.php/topic,7142.0.html

Is it this one? Mao explained it pretty well (I tried but failed I think!)
Title: Re: addition- multiplication of ordinates
Post by: kurrymuncher on November 06, 2008, 07:46:33 pm: yes it is, :)

i forgot that the graphs had equations.

thanks lulu
Title: Re: addition- multiplication of ordinates
Post by: dekoyl on November 06, 2008, 08:04:43 pm: I'm pretty sure you just multiply the y-values.

But I have a similar question..

How do you know the shape if it gives you f(x) and g(x) and tells you to do f(g(x))? Note that it doesnt result something easy like a quadratic.
I know how to do it with calculator but I think I've seen this on a Exam 1.. not too sure (mind playing tricks.)
Title: Re: addition- multiplication of ordinates
Post by: kurrymuncher on November 06, 2008, 08:14:07 pm: one more question-

Would they put transformations of matrices on exam 1, like finding x' and y' and all the dilations.
Title: Re: addition- multiplication of ordinates
Post by: /0 on November 06, 2008, 08:25:10 pm: Quote from: dekoyl on November 06, 2008, 08:04:43 pm
I'm pretty sure you just multiply the y-values.

But I have a similar question..

How do you know the shape if it gives you f(x) and g(x) and tells you to do f(g(x))? Note that it doesnt result something easy like a quadratic.
I know how to do it with calculator but I think I've seen this on a Exam 1.. not too sure (mind playing tricks.)

Think of f(x) as a 'transformation function'. i.e. applly the appropriate transformations to g(x).

e.g. $f(x) = \sqrt{x}-1$ , $g(x) = e^x+3$

$f(g(x)) = \sqrt{e^x+3}-1$

It's going to be the $y=e^x+3$ graph, only square rooted (remember if you take the square root of a number between 0 and 1 it becomes bigger) and translated 1 down.
Title: Re: addition- multiplication of ordinates
Post by: dekoyl on November 06, 2008, 08:32:07 pm: Thank you /0. You understand this so well. :)
(Sorry can't karma again)