HSC 2007 Question 10 (b) - help? (1 Viewer)

[akukei]

I have an assesment on this topic tomorrow and this question has stumped me... Anyone know how to do it?

http://www.boardofstudies.nsw.edu.au/hsc_exams/exam-papers-2007/pdf_doc/maths-07.pdf

 

[undalay]

(i) N = L/d^2
sum N = L/x^2 + L/(m-x)^2

(ii) differentiate with respect to x and solve normally (m and l are constants)

 

[akukei]

(i) N = L/d^2
sum N = L/x^2 + L/(m-x)^2

(ii) differentiate with respect to x and solve normally (m and l are constants)

I get lost when trying to solve for x after finding the derivative. Would you be able to post the working or the final answer?

 

[me121]

I get lost when trying to solve for x after finding the derivative. Would you be able to post the working or the final answer?

lol, that is the final answer.

You don't need to make it x =, you just need to have an expression for sum N , with x's on the other side.

EDIT: ohh.. were you reffering to part i or ii, I assumed you were talking about i.

 

[Iruka]

I am attaching my solution to this question.

View attachment 16320

 

[lyounamu]

I am attaching my solution to this question.

View attachment 16320

Iruka, my solution is basically same as yours but I had L1 above L2 so the working out is slightly altered like this:

x = (m . root(L1/L2))/(1+ root(L1/L2)) where root means "root 3".

I think they are basically same but your one looks more neat. Do you think mine is still correct? Or would I incur a loss of mark due to this?