A-level maths help :(

How would I do part b)? I got the right answer for part a btw because I know you obviously need to use it for part b). Any help would be much appreciated.

(edited 11 months ago)

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Reply 1

davros

Original post by skyeforster15

How would I do part b)? I got the right answer for part a btw because I know you obviously need to use it for part b). Any help would be much appreciated.

Post what you got for dy/dx and we can take it from there

Edit: note when you do dy/dx you get (something)^2 on the bottom which won't affect when it's < 0 :smile:

(edited 11 months ago)

Reply 2

BOSSMANnSMOKE

Original post by skyeforster15

How would I do part b)? I got the right answer for part a btw because I know you obviously need to use it for part b). Any help would be much appreciated.

wouldn't u just split the fraction so numerator<0 and denominator<0 then solve for x n keep in that format.

Reply 3

BOSSMANnSMOKE

Original post by davros

Post what you got for dy/dx and we can take it from there

Edit: note when you do dy/dx you get (something)^2 on the bottom which won't affect when it's < 0 :smile:

it's (20-4x^2)/(x^2 +5)^2
i think

Reply 4

skyeforster15

Original post by BOSSMANnSMOKE

it's (20-4x^2)/(x^2 +5)^2
i think

It is. Well thats what I got.

Reply 5

skyeforster15

I got +/- the square root of 5. Between that range.

(edited 11 months ago)

Reply 6

BOSSMANnSMOKE

Original post by skyeforster15

I got +/- the square root of 5. Between that range.

yh thats wt i got is that the answer?

Reply 7

skyeforster15

Original post by BOSSMANnSMOKE

yh thats wt i got is that the answer?

I was meant to say outside of that range because it is a negative quadratic.

Reply 8

davros

Original post by skyeforster15

I was meant to say outside of that range because it is a negative quadratic.

haven't checked your derivative, but yes if it's correct then you just need 20 - 4x^2 < 0 so 20 < 4x^2 or 5 < X^2 so you want the values of x < -root(5) or x > +root(5) :smile: