IGCSE/GCSE/O & A Level/IB/University Student Forum

Qualification => Subject Doubts => GCE AS & A2 Level => Math => Topic started by: Dania on October 03, 2010, 06:42:24 pm

Title: Functions Question
Post by: Dania on October 03, 2010, 06:42:24 pm
The function h is defined by: h:x = 6x-x2 for x [is greater than or equal] to 3

Express 6x-x2 in the form a-(x-b)2, where a and b are positive constants.

How would I go about such questions? I've seen them in quite a number of past papers.
Title: Re: Functions Question
Post by: nid404 on October 03, 2010, 06:50:50 pm
completing the square method.

http://en.wikipedia.org/wiki/Completing_the_square

So in this case

(x-3)2= x2-6x+9

so -x2+6x can be written as 9-(x-3)2
Title: Re: Functions Question
Post by: Dania on October 03, 2010, 07:03:37 pm
As always, thank you. :)
Title: Re: Functions Question
Post by: S.M.A.T on October 03, 2010, 07:09:32 pm
Quote from: Garfield on October 03, 2010, 06:50:50 pm
completing the square method.

http://en.wikipedia.org/wiki/Completing_the_square

So in this case

(x-3)2= x2-6x+9

so -x2+6x can be written as 9-(x-3)2

+rep for the fat cat :D
Title: Re: Functions Question
Post by: nid404 on October 03, 2010, 07:11:27 pm
You're welcome :)

thanks asif...and congrats ;)