VCE Methods Question Thread!

[IndefatigableLover]

1. Significant figures is NOT covered in the methods curriculum - in fact, you should be leaving all your answers in exact form unless the question states not to (eg, "round your answer to two decimal places")

2. That's a tricky question, because it depends on what you're actually doing. For example, in probability you might be asked to find the expected value of X (E[X]) of some data, and it might not seem correct to use decimal places given your data, however in this situation it IS correct to use decimal places.

However, given a modelling question with population counts, you should round down. So, just think about what you're doing, and just apply common sense as to if you should round down or not.

Ooh thanks for the quick reply EulerFan101! I haven't started on probability yet so the 'expected value of X' is a tad confusing for me LOL but I'll keep this in mind when I start on it! Actually 2 more days left of the holidays... might try and sneak some in there to understand what it is I guess :3

[keltingmeith]

I wouldn't worry too much - the expected value of X is just a fancy way of saying the mean. Probably (heheh, get it?) best that you spend the last couple of days resting anyway, hahah.

[jessss0407]

Hey guys! How do I differentiate log_e[1/(1-5x)]?

Thanks!

[achre]

Let ,  .
Then is just going to be the derivative of the inside function, g'(x), multiplied by the derivative of the outside function composed with the inside function, f' o g(x).

Spoiler

So and
Multiplying:
But! As the inside of a log has to be greater than 0, our original function had an implied domain of . So if you sketch the derivative, you only include the left branch of the curve.

[Orb]

Let ,  .
Then is just going to be the derivative of the inside function, g'(x), multiplied by the derivative of the outside function composed with the inside function, f' o g(x).

Spoiler

So and
Multiplying:
But! As the inside of a log has to be greater than 0, our original function had an implied domain of . So if you sketch the derivative, you only include the left branch of the curve.

^great working, it never occurred to me how you could utilise composite functions to solve the question

But you could also make it loge(1) - loge(1-5x)
loge(1) is 0, and then just differentiate -loge(1-5x) = 1/1-5x

[achre]

^ or do that, that's better, I'm just an arts student trying to learn latex.

[Jawnle]

How do I plot points on a CAS? Thanks

[Rishi97]

How do I plot points on a CAS? Thanks

On th home pg, go to lists and spreadsheet.
Then write your x and y values
Don't forget to label the columns at the top
Then go back to the home pg and go on data and statistics. Move your cursor over the bottom of the pg and click "click to add variable". Choose the one that you labelled your graph with. Do the same for the yaxis.
Hope I made sense

[paper-back]

Just to get it confirmed
When I have to graph an equation such as this:

I'm actually translating it units right not units right, right?

And the same goes for cos and tan?

[rhinwarr]

Yes, you always have to factorise out the co-efficient of x so it would become sin(3(x-pi/6))

[Jawnle]

On th home pg, go to lists and spreadsheet.
Then write your x and y values
Don't forget to label the columns at the top
Then go back to the home pg and go on data and statistics. Move your cursor over the bottom of the pg and click "click to add variable". Choose the one that you labelled your graph with. Do the same for the yaxis.
Hope I made sense

Yesss thankyou

[paper-back]

Thanks rhinwarr

[nerdmmb]

Would really appreciate some help with this question.

Consider the quadratic equation (-2p+1)x²+(p-2)x+6p=0

For p≠1/2, show that there are always two rational solutions and find these solutions.


I tried solving the discriminant and there was only 1 solution because the discriminant was a perfect square so  I'm confused..

[kinslayer]

Would really appreciate some help with this question.

Consider the quadratic equation (-2p+1)x²+(p-2)x+6p=0

For p≠1/2, show that there are always two rational solutions and find these solutions.


I tried solving the discriminant and there was only 1 solution because the discriminant was a perfect square so  I'm confused..

I get the discriminant as . It's a quadratic with turning point on the x-axis so there will be two solutions if . Dunno if I'm going crazy or what, but the statement as written in the question looks wrong to me.

[nerdmmb]

I get the discriminant as . It's a quadratic with turning point on the x-axis so there will be two solutions if . Dunno if I'm going crazy or what, but the statement as written in the question looks wrong to me.

Yes I also got that discriminant I'm glad I'm not the only one who thought the question is wrong.
I also don't understand why the question asks for two rational solutions when the discriminant is a perfect square.