Easy Question 10 or Easiest? (1 Viewer)

[betraya]

I did it by y= integral of xlnx-x and replacing by x-2 for 10a). Took 2 + pages for proving 10b i and ii

 

[wozzame]

10b got it all but for a, was it a trick? How did we do it?

Since we don't know how to integrate a log, you needed to basically turn the whole thing on it's side and integrate under the curve bounded by the y-axis.

Basic run-through on how to do it:
- Get the equation in terms of x. I don't have the paper in front of me, but I think you end up with something like x = e^y + 2
- Integrate(between 0 and ln5) e^y + 2, dy. This finds the area to the left of the curve (i.e. from the curve to the y-axis)
- Take this integral away from the rectangle area(ln 5 * 7).

 

[LoneWolf1990]

10 a was easy

10 b got me good
i couldnt find the area of the upper triangle :S

To find the area of the upper triangle, what you could have done was use the similar triangles ratio formula to obtain an expression for line MP, then add the areas

 

[pyjamapants]

I wouldn't say question ten was easy. It was pretty challenging question. Especially for the 2 uniters.
Plus, I've seen easier ones in past papers.

 

[dolbinau]

Damn for 10a I just said the unshaded area was the answer how many marks would I get?

 

[BackCountrySnow]

oh what?
there was a question 10??

 

[karnage]

Oh fuck, i was just thinking back to Q10b and i got the differentiation wrong!

So, would i still get any marks if i had the correct process but ended up with the wrong x value?

 

[Smeegen999]

My minimum value of x was l/root 2 iirc

The length was a like root something minus soomething times x

i got that.

exam was easy as! hoping to get 95-105/120 raw

 

[nevdoggz]

thought it was fairly easy

hoping for +95%

 

[zxcvbee]

Loved it! i toatally got it! so glad about that cos ive been screwing up my other exams, so glad i got maths to fall back on.. haha yay

 

[m.incognito]

Damn for 10a I just said the unshaded area was the answer how many marks would I get?

hahaha holy shit i think i did that too.
i'd say 4/5? only one step missing...

 

[Arithela]

For 10a I did the worst mistake!

I found the area of the rectangle (7ln5) and area between the curve and x-axis by using simpson's rule

then total area = area of rectangle - value of simspon's rule

 

[old.skool.kid]

Wait so was 10a supossed to be bound by the x-axis or y-axis?
Damn i think i stuffed it.

 

[zabzoub1]

THE EASIEST 2unit TEST EVER!!!!!! LOL

 

[aussiechick007]

lol i got um .... nothing for 10a... but i did a heap for 10b .... and i think i did well on the rest of the paper...

 

[smozdaddy]

OK so im not sure if it was correct but i think my final answer for 10a was:

5ln5 - 4.

This sound right?

 

[pissedoff]

OK so im not sure if it was correct but i think my final answer for 10a was:

5ln5 - 4.

This sound right?

yes

 

[pyjamapants]

Shit.
For 10 a, I made one of my boundaries 5 instead of ln5.
Bugger.
Btw, what justifcation did you use for x being l/rt2 ???
I had something pathetic like the ratio of x to l had to be greater than one otherwise the gate wouldn't intersect. But I know it's wrong.

 

[Ovidiu]

thts wat i got and a friend hopefully it tis

 

[karnage]

Btw, what justifcation did you use for x being l/rt2 ???
I had something pathetic like the ratio of x to l had to be greater than one otherwise the gate wouldn't intersect. But I know it's wrong.

???

You had to find the second derivative, and use it as a test point to prove its the minimum value.