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December 03, 2020, 08:23:20 am

Author Topic: VCE Methods Question Thread!  (Read 3081182 times)  Share 

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keltingmeith

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Re: VCE Methods Question Thread!
« Reply #18795 on: September 18, 2020, 08:30:28 pm »
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Replied faster than I could edit lol

Cool cool. So the next step is obviously going to be showing that for x>2, f'(x)<0, what have you done in trying to show this?
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Corey King

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Re: VCE Methods Question Thread!
« Reply #18796 on: September 19, 2020, 12:59:30 pm »
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Hey guys, stuck on another question :)
This one on gradients, but I'm struggling with the algebra. I'm not sure how to find the gradient for Q5 b.

https://gyazo.com/de839352a3792618cd683391ffe8e81c

I fiddled around a bit but don't know how to find the solution. The answer book says it is 2/5.


Sine

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Re: VCE Methods Question Thread!
« Reply #18797 on: September 19, 2020, 01:14:09 pm »
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Hey guys, stuck on another question :)
This one on gradients, but I'm struggling with the algebra. I'm not sure how to find the gradient for Q5 b.

https://gyazo.com/de839352a3792618cd683391ffe8e81c

I fiddled around a bit but don't know how to find the solution. The answer book says it is 2/5.


I think you just need to factor out (b-a) from both the numerator and the denominator and let them cancel each other out to leave 2/5. Although this assumes a=/=b

S_R_K

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Re: VCE Methods Question Thread!
« Reply #18798 on: September 19, 2020, 03:38:47 pm »
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Although this assumes a=/=b

Which is reasonable, otherwise the question doesn't uniquely define a line.

Corey King

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Re: VCE Methods Question Thread!
« Reply #18799 on: September 19, 2020, 06:37:35 pm »
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I think you just need to factor out (b-a) from both the numerator and the denominator and let them cancel each other out to leave 2/5. Although this assumes a=/=b

Yeap, it seems to simple now :)
Factorizing seems to be a weak point of mine.
Thank you!
Corey

Corey King

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Re: VCE Methods Question Thread!
« Reply #18800 on: September 22, 2020, 01:51:27 pm »
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Hey guys :)
Do you know what the m stands for before the angle sign in:
https://gyazo.com/f6167e435f2d47ac94291f119684d634

keltingmeith

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Re: VCE Methods Question Thread!
« Reply #18802 on: September 22, 2020, 05:18:01 pm »
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A.

I do not understand how t=-1 is considered a solution.

Thanks
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keltingmeith

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Re: VCE Methods Question Thread!
« Reply #18803 on: September 22, 2020, 05:57:04 pm »
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A.

I do not understand how t=-1 is considered a solution.

Thanks

I mean.

You let x_1=x_2, you end up with a quadratic in t, you should get two answers. Presumably this is how you found the first answer. What's your argument for why t can't equal -1?
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Re: VCE Methods Question Thread!
« Reply #18804 on: September 22, 2020, 06:04:07 pm »
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I mean.

You let x_1=x_2, you end up with a quadratic in t, you should get two answers. Presumably this is how you found the first answer. What's your argument for why t can't equal -1?
t represents time in seconds, and time cannot be negative, so I would assume you reject t=-1 as a solution and take only the other solution.

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Re: VCE Methods Question Thread!
« Reply #18805 on: September 22, 2020, 06:08:56 pm »
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I mean.

You let x_1=x_2, you end up with a quadratic in t, you should get two answers. Presumably this is how you found the first answer. What's your argument for why t can't equal -1?
-1 seconds. That doesn't make any sense.
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keltingmeith

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Re: VCE Methods Question Thread!
« Reply #18806 on: September 22, 2020, 06:29:08 pm »
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t represents time in seconds, and time cannot be negative, so I would assume you reject t=-1 as a solution and take only the other solution.

-1 seconds. That doesn't make any sense.

Doesn't it? Here's a question - what if I want to know how long I have to wait until you reply to my previous post? Well, you already have replied, so I'd have to wait -11 minutes. OR what if I want to know how long until my pizza is ready to eat 5 minutes after it's finished cooking? Well, it was ready 5 minutes ago, so I'd have to wait -5 minutes. And an example maybe a bit more relevant to the question: if I arrive to a bus stop 5 minutes after the bus has, and the next one is in 20 minutes, at what times will a bus arrive? Either 5 minutes ago, or 20 minutes from now.

You both have assumed that because t is time, it cannot be negative - but why not? All we know is that we started the timer when x_1 was at position 2, and x_2 was at position -2. That doesn't mean they were ALWAYS at those positions, that's just the positions at which we started the timer. At no point did the question say that t HAD to be greater than 0 - you guys assumed this.

In fact, if you look at any VCAA exam where t is the time, they will ALWAYS specify a domain for t. Sure, /usually/ that domain is just t>0, and I don't think there's been a case yet where it could be negative (there probably is one in some normal distribution question that I'm missing - tbh I went straight to the specialist exams, because they mention time more), but that doesn't mean it can be negative. Time is just a relative construct, after all.

Potentially another analogy that might help - let's say I'm cooking pizza, it takes 10 minutes to cook, but I don't start the timer until 3 minutes after I put it in the oven. Does that mean that I still take the pizza out when the timer says it's been 10 minutes? Of course not, my pizza will be burnt - I'd take it out at 7 minutes, because -3+10=7. You could even say that I, the person, will position myself at the oven at the times t=-3 and t=7 minutes.

EDIT: Also, fun fact, the file name for the 2018 specialist exam 2 is "2016 Specialist Mathematics Written examination 2" lmfao
« Last Edit: September 22, 2020, 06:36:10 pm by keltingmeith »
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Re: VCE Methods Question Thread!
« Reply #18807 on: September 23, 2020, 06:00:59 am »
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Can someone help me predict a study score for this year please?

SAC: 81% U3, 88% U4
Both SAC scores were in the upper range of the upper quartile. So I'm probably in the top 5 of a medium cohort.

Exam Scores Prediction:
E1: 35/40
E2: 65/80

I go to a private school but the cohort is not the strongest. For methods there are 39 people in my cohort sitting methods. I just need to know if I can get above 40 with this and hopefully if 45 is still in reach. Thank you so much! :)

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Re: VCE Methods Question Thread!
« Reply #18808 on: September 23, 2020, 09:46:09 am »
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Hi and welcome to the forums!
This isn't the place to go to for study scores; try clicking on the link in keltingmeith's signature instead to get there.
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Re: VCE Methods Question Thread!
« Reply #18809 on: September 23, 2020, 04:00:47 pm »
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you know what, **** it. first I had failed security checks then it said i already posted, but i didn't, and then it said IP address try again later.

here's the question copy and pasted from elsewhere.

The graph of the function y=x^4−12x^3 is translated by a units in the positive direction of the x-axis and b units in the positive direction of the y-axis (where a and b are positive constants).
a) Find the coordinates of the turning points of the graph of y=x^4−12x^3.
b) Find the coordinates of the turning points of its image.

specifically b.
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