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October 17, 2025, 12:39:02 am

Author Topic: VCE Methods Question Thread!  (Read 5740120 times)  Share 

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alchemy

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Re: VCE Methods Question Thread!
« Reply #3375 on: December 26, 2013, 01:27:50 pm »
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guys theres a 12b for the answer of that question?

Sorry, what do you mean?

Only Cheating Yourself

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Re: VCE Methods Question Thread!
« Reply #3376 on: December 26, 2013, 02:02:40 pm »
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Sorry, what do you mean?

for this question

Find the distance between each of the following pairs of points in terms of the given variables

(5,b) (0,6)
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Sup

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Re: VCE Methods Question Thread!
« Reply #3377 on: December 26, 2013, 04:12:07 pm »
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Why are you doing so much maths during the early parts of the holidays? Chill out...

Only Cheating Yourself

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Re: VCE Methods Question Thread!
« Reply #3378 on: December 26, 2013, 07:16:36 pm »
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A piggybank contains 67 coins.  If there are only one and two dollar coins in the piggybank.  And there are 25 more one dollar coins than two dollar coins, how many of each are there.

theres are  the questions i struggle with!  I know i have to form a simultaneous equation or so i think but i have no clue!  I not the answer minus the working out but theres are the questions i need improvement in, can anyone help me?

Thanks
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Tasmania Jones

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Re: VCE Methods Question Thread!
« Reply #3379 on: December 26, 2013, 07:40:31 pm »
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Let = number of $1 coins
Let = number of $2 coins

If there are 67 coins in total, then this is the first equation.

There are 25 more $1 coins than $2 coins so this is the second equation.
Solve these equations but putting equation 2 into equation one (substitute for )
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Only Cheating Yourself

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Re: VCE Methods Question Thread!
« Reply #3380 on: December 26, 2013, 07:57:28 pm »
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Let = number of $1 coins
Let = number of $2 coins

If there are 67 coins in total, then this is the first equation.

There are 25 more $1 coins than $2 coins so this is the second equation.
Solve these equations but putting equation 2 into equation one (substitute for )

yea i did that, but i still couldn't get right answer.
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Tasmania Jones

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Re: VCE Methods Question Thread!
« Reply #3381 on: December 26, 2013, 08:00:12 pm »
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Did you get 21 $2 coins and 46 $1 coins? What's the answer?
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Snorlax

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Re: VCE Methods Question Thread!
« Reply #3382 on: December 26, 2013, 08:20:56 pm »
+1
yea i did that, but i still couldn't get right answer.

It's just very simple substitution.
x+y=67
y+25=x

2y+25=67
y=21


to get x, substitute back y=21:
x+21=67
x=46

therefore, there are 46 one dollar coins, and 21 two dollar coins.
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Re: VCE Methods Question Thread!
« Reply #3383 on: December 26, 2013, 11:33:42 pm »
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Hey guys,
Could I please have a detailed explanation of how to sketch the following function. And in particular how you found the intercept.
F(x)= |x - 3| +1
And
 f(x)= - |x - 3| + 1
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lzxnl

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Re: VCE Methods Question Thread!
« Reply #3384 on: December 26, 2013, 11:46:48 pm »
+5
Hey guys,
Could I please have a detailed explanation of how to sketch the following function. And in particular how you found the intercept.
F(x)= |x - 3| +1
And
 f(x)= - |x - 3| + 1

For the first one, consider the graph of y=|x|. It is a graph that looks V-shaped and is created by combining the second quadrant part of y=-x with the first quadrant part of y=x
Then, translate the graph three units to the right and one unit up; that's what F(x) is. Its new vertex is at (3,1) and the intercepts can be worked out similarly.

For f(x), you have a graph with the same vertex; the only difference is that the straight lines point in a different direction. Make them point downwards instead of upwards as with F(x)

The way I sketch these is as follows:

Firstly, observe if the coefficient of the |x-a| term is positive or negative. This determines whether the graph points up or down.
Secondly, work out the intercepts; F(0)=|-3|+1=4, so y intercept is (0,4). F(x) is never equal to zero as F(x) is the sum of a positive number and a non-negative number; it is always larger than zero, so no x intercepts. So, I have the y-intercept and the vertex. Draw a straight line through those, and stop the line at the vertex. Then, try and draw a mirror image of the line you just drew.
For f(x), f(0)=-3+1=-2, so the y intercept is (0,-2). There are two x-intercepts: f(x)=0
|x-3|=1, (x-3)^2=1, x= 4 or 2. So graph passes through (2,0) and (4,0). Mark all three intercepts on the graph.
Then, note the vertex of (3,1). You want to draw straight lines from each x intercept to the vertex, and then stop at the vertex. You'll have your V-shape then
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Re: VCE Methods Question Thread!
« Reply #3385 on: December 26, 2013, 11:54:35 pm »
+6
The modulus will take any negative number, and make it into a positive number of the same magnitude, and leave everything else as in. This means that when we apply the modulus to , we are effectively taking the region of the graph for which , that is it is below the axis and flipping in the axis, (I should note this only applies when we apply the modulus to the outside of a function, i.e. , the case where it is applied to the inside of a function, i.e. is different). Then for the graph above we'll shift that resulting graph upwards by one unit.
For the and intercepts, we have

Now if , (so ) then the modulus won't do anything to out line. If (so ), then our line is flipped, and we need to include a negative, as we effectively have

So as our solutions don't satisfy each particular part we don't have an intercepts, but we do have a intercept at .

Now the only part we are missing is the sharp point, as we know that the sharp point of is at , then applying the transformations we get the sharp point at (you could also look at this by solving what is inside the modulus and equating that to zero, as this is where our original curve is 'flipped').

So applying the transformations one by one we have:







With the second, follow the same method, just remember to have that negative in there.

Hope that helps! I feel I may have explained it in a round about way merging two methods.... but hope you take something from it anyways.

EDIT: Beaten, shouldn't have spent time in plotting the graphs :P
« Last Edit: December 26, 2013, 11:58:46 pm by b^3 »
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Only Cheating Yourself

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Re: VCE Methods Question Thread!
« Reply #3386 on: December 27, 2013, 04:10:47 pm »
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Polynomials.  Anything i should know about as i'm starting it.
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Re: VCE Methods Question Thread!
« Reply #3387 on: December 27, 2013, 07:24:26 pm »
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This is my first time doing these types of graphs and Im a bit confused...
Why can |2x + 3| be written as both (2x + 3) or −(2x + 3)?

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Re: VCE Methods Question Thread!
« Reply #3388 on: December 27, 2013, 07:33:43 pm »
+1
Firstly we note that the modulus function will give a positive number of the same magnitude of our original number. e.g. and . This, when applied to a whole function effectively flips all the parts of our curve that are below the axis, in and over the axes.

If , (so )that is the curve is above (well including zero) the axis, then will be the same as , as we know that is positive for this domain and so the modulus has no effect.

If , (so that is the curve is below the axis, then will be the same as . This is because we know that is negative for this domain, so for the modulus to make it positive but of the same magnitude, we need to multiply it by a negative 1. i.e. -ve*-ve=+ve.

So we have the following:

« Last Edit: December 27, 2013, 07:36:19 pm by b^3 »
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Strawberrry

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Re: VCE Methods Question Thread!
« Reply #3389 on: December 27, 2013, 11:25:11 pm »
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Thank you b^3, that makes so much more sense   ;D

Where do you find the modulus symbol | on a CAS calc?