A Level Maths Exam Question

https://www.quora.com/profile/Bravewarrior/p-158771216
Here is the question. I am stuck on part b. Would really appreciate some help!

Reply 1

roantpp

Original post by pigeonwarrior

https://www.quora.com/profile/Bravewarrior/p-158771216
Here is the question. I am stuck on part b. Would really appreciate some help!

a must be > 0 so b^2/b-1 must also be above 0. b^2 term is always positive so we dont worry bout that. therefore b-1 > 0 so b>1 so final restriction is 1<b<a .

Reply 2

tonyiptony

Well, what do you think?

Reply 3

pigeonwarrior

Original post by roantpp

a must be > 0 so b^2/b-1 must also be above 0. b^2 term is always positive so we dont worry bout that. therefore b-1 > 0 so b>1 so final restriction is 1<b<a .

Thank you so much! 😀

Reply 4

pigeonwarrior

Original post by tonyiptony

Well, what do you think?

I got to the stage where I did b^2/b-1 > 0 but I did b^2>0 which obviously did not get me anywhere. So the only other thing I could do was b-1>0 but I was not sure if this was right, and if so why

Reply 5

tonyiptony

Original post by pigeonwarrior

I got to the stage where I did b^2/b-1 > 0 but I did b^2>0 which obviously did not get me anywhere. So the only other thing I could do was b-1>0 but I was not sure if this was right, and if so why

The idea is to check "what values of b would make your calculation (in)valid" at every step.
So read from the very beginning of the question and analyze at every step - including the given!

Also b-1>0 is not quite right, I think.