VCE Methods Question Thread!

[keltingmeith]

Ah, my bad! Here it is (hopefully) 

For questions like these, I highly recommend using this tool. Simply enter your expression into the box (write it as (x^2+2)/(sqrt(x)), but there's also buttons there to help if you're unsure how to write some more complicated stuff). You can then click "show steps" to see how they've done it step-wise, and put your mouse over the derivatives in the step-wise solution to see what derivative laws they've used.

[Jigsaw]

For questions like these, I highly recommend using this tool. Simply enter your expression into the box (write it as (x^2+2)/(sqrt(x)), but there's also buttons there to help if you're unsure how to write some more complicated stuff). You can then click "show steps" to see how they've done it step-wise, and put your mouse over the derivatives in the step-wise solution to see what derivative laws they've used.

Thank you very much for introducing this to me! I've just used it and have figured out my mistake from the step-by-step solutions!

[Rieko Ioane]

Hi,

Could I have help with this question? https://imgur.com/a/lMus0
The answer says the function must have a period of Pi to satisfy the equation which I don't understand.
I don't understand how the answer is E intuitively?

Note: I understand I can just use trial and error but I want to know how to do it 'properly'.

[Bri MT]

Hi,

Could I have help with this question? https://imgur.com/a/lMus0
The answer says the function must have a period of Pi to satisfy the equation which I don't understand.
I don't understand how the answer is E intuitively?

Note: I understand I can just use trial and error but I want to know how to do it 'properly'.

Maybe try this: Draw up a graph and make it so that the graph has the same y-value when pi is added or subtracted  to the x value. From your graph, determine the period

[Rieko Ioane]

Maybe try this: Draw up a graph and make it so that the graph has the same y-value when pi is added or subtracted  to the x value. From your graph, determine the period

Ah right, guess I was over complicating this. Thanks.

For this question,https://imgur.com/a/6vTcb

For part iii: they have x=29 and n=100 from the information given in part c. But at the start of the question they tell us 20% of the people in the area have tooth decay, so I used x=20, n=100.

What part of the question species if we have to use x=29 or x=20?

[Yueni]

Hi,

Could I have help with this question? https://imgur.com/a/lMus0
The answer says the function must have a period of Pi to satisfy the equation which I don't understand.
I don't understand how the answer is E intuitively?

Note: I understand I can just use trial and error but I want to know how to do it 'properly'.

Simply speaking, cos(2(x-pi))=cos(2x), therefore for all values of u it will satisfy the equation f(u)=f(u-pi)

[Yueni]

Ah right, guess I was over complicating this. Thanks.

For this question,https://imgur.com/a/6vTcb

For part iii: they have x=29 and n=100 from the information given in part c. But at the start of the question they tell us 20% of the people in the area have tooth decay, so I used x=20, n=100.

What part of the question species if we have to use x=29 or x=20?

Recall that confidence intervals are calculated from sample data only. That is, phat and not p. So, in this case, phat = 29/100 and n=100

[Rieko Ioane]

Thanks everyone for helping me.

I've got another question tho, soz..

For part b of this question https://imgur.com/a/0ya04

Why do we need to use pythag to find the magnitude when these functions are already defined as the distance? The context of this question is 2 cars moving towards the origin starting 100km along the X-axis and y-axis respectively.

[VanillaRice]

Thanks everyone for helping me.

I've got another question tho, soz..

For part b of this question https://imgur.com/a/0ya04

Why do we need to use pythag to find the magnitude when these functions are already defined as the distance? The context of this question is 2 cars moving towards the origin starting 100km along the X-axis and y-axis respectively.

When you subtracted d_A - d_B, you are actually finding the difference in the distance that they have travelled. For example, say car A has moved 10km, while car B has only moved 2km in the same amount of time. d_A - d_B = 8km, which means car A has travelled 8km more than car B. This does not necessarily imply they are 8km away from each other.
We can use Pythagoras' theorem because the x and y-axis form a right-angled triangle, with the distance between the two cars being the hypotenuse.

Hope this helps

[TheCommando]

https://imgur.com/a/Dztll
His is the answers wronng
Why do i do 0.9 when the wuestions asks to find at leastt 0.85

Also how do i do eiii
https://imgur.com/a/WGLFb

MOD EDIT: double post merged

[Sine]

https://imgur.com/a/Dztll
His is the answers wronng
Why do i do 0.9 when the wuestions asks to find at leastt 0.85

Also how do i do eiii
https://imgur.com/a/WGLFb

MOD EDIT: double post merged

you use 0.9 since p = 0.9 the proportion of "regular" strawberries. The 0.85 has already been accounted for since you converted that to actual number of strawberries.

Also remember to never write down calculator sytax during a test or exam e.g. binomCdf(x₀, x₁, x₃, x₄ )


For eiii

You need to do what the asked "use the normal approximation"  which is

.

so now we have the mean and variance (hence standard deviation) of the population proportion so now now since they say "use normal approximation" we use it otherwise we would need to know that n is sufficiently large enough for this approximation. Now we can just use the standard technique to convert to standard normal for whatever range of values we require.

[TheCommando]

you use 0.9 since p = 0.9 the proportion of "regular" strawberries. The 0.85 has already been accounted for since you converted that to actual number of strawberries.

Also remember to never write down calculator sytax during a test or exam e.g. binomCdf(x₀, x₁, x₃, x₄ )


For eiii

You need to do what the asked "use the normal approximation"  which is

.

so now we have the mean and variance (hence standard deviation) of the population proportion so now now since they say "use normal approximation" we use it otherwise we would need to know that n is sufficiently large enough for this approximation. Now we can just use the standard technique to convert to standard normal for whatever range of values we require.

So what does my workin out look like
I dont know what im meant to write down

[Sine]

So what does my workin out look like
I dont know what im meant to write down

is what you've written your working out or just the suggested solutions?

[Rieko Ioane]

Hi,

For this https://imgur.com/a/9CiWf

Part c) so I have g(x) = (m-n)/(x+n)+1. I got n=-1 and m E R which is almost correct, except m excludes -1,0. I don't know why -1 is excluded tho? It doesn't cause any problems if m=-1 does it?

f) apart from their intersection on the line y=x, how do I get the other intersections in exact form? I solved w = w^-1 with my TI but it does not solve it for exact values.

[Shadowxo]

Hi,

For this https://imgur.com/a/9CiWf

Part c) so I have g(x) = (m-n)/(x+n)+1. I got n=-1 and m E R which is almost correct, except m excludes -1,0. I don't know why -1 is excluded tho? It doesn't cause any problems if m=-1 does it?

f) apart from their intersection on the line y=x, how do I get the other intersections in exact form? I solved w = w^-1 with my TI but it does not solve it for exact values.

But, if m=-1 then g(x)=1 and its inverse can't be found this way. Remember, the inverse is basically the function flipped around the line y=x so the inverse function would be x=1 (so technically isn't a function). There needs to be an x and y to switch around to find the inverse like that

For f), I would think you'd work the inverse out by hand and make w and w^-1 equal to find the coordinates. If it's a calculator test/exam though I wouldn't think they'd take marks off for it not being exact values unless they specified in the question.