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MAT Prep Thread - 2nd November 2016

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Original post by dfbenjamin
For that I got (x+a/2)^2 + (y+b/2)^ = c + (a+b)/4

This is a circle with radius (c + (a+b)/4)^(1/2), centre (-a/2, -b/2)

So the origin is ((a/2)^2 + (b/2)^2)^(1/2) away from the centre

so c + a/4 + b/4 > a^2/4 + b^2/4
so 4c > a^2 + b^2 + a + b

what have I done wrong here?


Ya I got the answer with 4c in it.
Original post by AmanGottu
Ya I got the answer with 4c in it.


yeah but the answer with 4c was just 4c>a^2 + b^2

it didn't have the a + b as well
Original post by dfbenjamin
For that I got (x+a/2)^2 + (y+b/2)^ = c + (a+b)/4

This is a circle with radius (c + (a+b)/4)^(1/2), centre (-a/2, -b/2)

So the origin is ((a/2)^2 + (b/2)^2)^(1/2) away from the centre

so c + a/4 + b/4 > a^2/4 + b^2/4
so 4c > a^2 + b^2 + a + b

what have I done wrong here?


on the very first line when you complete the square it should be c+(a^2+b^2)/4
I got c>0 (or was it c<0? the inequality with only c in).
Original post by dfbenjamin
yeah but the answer with 4c was just 4c>a^2 + b^2

it didn't have the a + b as well


I just remember when working the problem, it made sense and I was pretty sure that was right... Do you know what the right answer is?
Original post by dfbenjamin
For that I got (x+a/2)^2 + (y+b/2)^ = c + (a+b)/4

This is a circle with radius (c + (a+b)/4)^(1/2), centre (-a/2, -b/2)

So the origin is ((a/2)^2 + (b/2)^2)^(1/2) away from the centre

so c + a/4 + b/4 > a^2/4 + b^2/4
so 4c > a^2 + b^2 + a + b

what have I done wrong here?


First line: should be (x+a/2)^2 + (y+b/2)^ = c + (a^2+b^2)/4
Original post by dfbenjamin
A^n(B^m(x))= (2^n)(3^n)x+(2^n*3^n - 1)

I never found this - would you mind explaining how it is derived?


This is just concerning the compound functions used in the last part - I don't know how this remains the same when the order of the As and Bs is muddled with, so I brute forced the 2nd last part to give the same result.IMG_20161103_185528.jpg
Original post by m0.4444
on the very first line when you complete the square it should be c+(a^2+b^2)/4


oh yeah of course forgot that (a/2)^2 = a^2/4

thanks!

and then everything cancels out (just noticed another mistake in the answer i posted here lol but I didn't make that mistake in the exam)
(edited 7 years ago)
Original post by dfbenjamin
oh yeah of course forgot that (a/2)^2 = a^2/4

thanks!

and then everything cancels out (just noticed another mistake in the answer i posted here lol but I didn't make that mistake in the exam)


Do you guys remember what the answer choices were for that question? Was there anything that said c could be anything? (I'm trying to think if I made a mistake by putting that answer choice or put c>0)
Original post by pressurize
Do you guys remember what the answer choices were for that question? Was there anything that said c could be anything? (I'm trying to think if I made a mistake by putting that answer choice or put c>0)


I know there was c>0, 4c>a^2 + b^2 and 4c<a^2 + b^2

not sure about what the other one was though
So was anyone able to get the explanation for the second last part of Q2, or the anything in the last part of Q2?
Original post by pressurize
Do you guys remember what the answer choices were for that question? Was there anything that said c could be anything? (I'm trying to think if I made a mistake by putting that answer choice or put c>0)


I immediately recognized c>0 but now im thinking i put c<0
Original post by m0.4444
I immediately recognized c>0 but now im thinking i put c<0


I thought there was just one inequality only with c?
Uggh now I think that I put c can be anything. Was that even an answer choice?
For Q5, if your reasoning is right and you wrote it down and you get the first half right but then you make a silly algebra mistake and get to an incorrect answer would you still get like method marks or something for the working/reasoning?
Original post by pressurize
Uggh now I think that I put c can be anything. Was that even an answer choice?


I'm almost certain they were all inequalities so I wouldn't worry
Original post by RuairiMorrissey
I thought there was just one inequality only with c?

Thats good then.
Reply 1437
Avatar for 11234
11234
8
For b did anyone put 2 + sqrt2.
Original post by dfbenjamin
I'm almost certain they were all inequalities so I wouldn't worry


But how many inequalities where there with c and 0.
Original post by 11234
For b did anyone put 2 + sqrt2.


i got that one wrong. But i think its 2 - sqrt2

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