Mathematics Question Thread

[12070]

I mean the former.

The answer just switches between the two.

[RuiAce]

I mean the former.

The answer just switches between the two.

Also don't forget that a 2 automatically appears from the trapezoidal rule formula, not from actually computing f((a+b)/2)

[12070]

Also don't forget that a 2 automatically appears from the trapezoidal rule formula, not from actually computing f((a+b)/2)
[/quote]

Ahhh. I completely missed the two. Thank you. So only when it's a log you can bring a power to the front?

[Opengangs]

Also don't forget that a 2 automatically appears from the trapezoidal rule formula, not from actually computing f((a+b)/2)


Ahhh. I completely missed the two. Thank you. So only when it's a log you can bring a power to the front?

If the power is inside, then you can bring it down.
For example, log(x^2) is the same as 2logx, but not the same as [log(x)]^2

[RuiAce]

Also don't forget that a 2 automatically appears from the trapezoidal rule formula, not from actually computing f((a+b)/2)


Ahhh. I completely missed the two. Thank you. So only when it's a log you can bring a power to the front?

If you're referring to the log law \( \log M^n = n \log M\) then yes

[biffi023]

Hey 
im warning u now that this might not make sense.. but hopefully i can kinda explain it! 
this is a question from 2016 hsc paper.. i finished working it out and got it right, but on looking back at it.. shouldn't you only have to rotate it 'half' of the way around, seeing as you are given the whole shape? like if you were given this same question but with only the 0<y<2 portion, wouldnt you use the same working and rotate it the whole way?
im just thinking that seeing as you have 2 symmetrical 'parts' of the same curve, both rotating that you would only have to rotate it half way around the x-axis for them to 'meet up' and form the whole volume?? btw.. im only really talking abt the 'C2' part of it.. C1 i just found using volume of a sphere formula..
but maybe my whole thinking is wrong!?? if someone can make that clear to me wld be awesome!!
thank u!

[gilliesb18]

Another one on derivatives using first principles (sorry )
f(x)= 2x^3 +5x
for some reason i keep getting 6x^3 +5, but the answer is 6x^2 +5 so i don't know how to get it.
Can someone help me once again???
Thanks...

[RuiAce]

Hey 
im warning u now that this might not make sense.. but hopefully i can kinda explain it! 
this is a question from 2016 hsc paper.. i finished working it out and got it right, but on looking back at it.. shouldn't you only have to rotate it 'half' of the way around, seeing as you are given the whole shape? like if you were given this same question but with only the 0<y<2 portion, wouldnt you use the same working and rotate it the whole way?
im just thinking that seeing as you have 2 symmetrical 'parts' of the same curve, both rotating that you would only have to rotate it half way around the x-axis for them to 'meet up' and form the whole volume?? btw.. im only really talking abt the 'C2' part of it.. C1 i just found using volume of a sphere formula..
but maybe my whole thinking is wrong!?? if someone can make that clear to me wld be awesome!!
thank u!

Subtleties are left to second year uni.

[RuiAce]

Another one on derivatives using first principles (sorry )
f(x)= 2x^3 +5x
for some reason i keep getting 6x^3 +5, but the answer is 6x^2 +5 so i don't know how to get it.
Can someone help me once again???
Thanks...

If you're having trouble, please post relevant working out.

[biffi023]

(Image removed from quote.)


Subtleties are left to second year uni.

ahh!! thanks so much 

[Mymy409]

How would you do this question?

Jenny puts aside $20 at the end of each month for 3 years. How much will she have at the end of the 3 years if the investment earns 8.2% per annum paid monthly.


I've seen superannuation questions where the investment is done at the beginning of the period, but not at the end.

[RuiAce]

How would you do this question?

Jenny puts aside $20 at the end of each month for 3 years. How much will she have at the end of the 3 years if the investment earns 8.2% per annum paid monthly.


I've seen superannuation questions where the investment is done at the beginning of the period, but not at the end.

[Mymy409]

Thanks, Rui

[Opengangs]

You will need to form a generalised equation for A_n, using geometric progression.
Hopefully, you're able to solve it from here.

(:

[RuiAce]

You will need to form a generalised equation for A_n, using geometric progression.
Hopefully, you're able to solve it from here.

(:

I presume they already knew that since they could handle deposits at the beginning of the year. I just illustrated the other one for means of contrast (because it was at the end of the year, i.e. we're considering an annuity in arrears as opposed to annuity in advance).