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Offline Dania

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Functions Question
« 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.
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nid404

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Re: Functions Question
« Reply #1 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
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Offline Dania

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Re: Functions Question
« Reply #2 on: October 03, 2010, 07:03:37 pm »
As always, thank you. :)
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Offline S.M.A.T

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Re: Functions Question
« Reply #3 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
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nid404

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Re: Functions Question
« Reply #4 on: October 03, 2010, 07:11:27 pm »
You're welcome :)

thanks asif...and congrats ;)
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