# GCSE Edexel maths completing the square

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#1
Why is it not 25/16 here, isn’t 5/4 squared 25/16, not 25/8?
Last edited by Mavs04; 1 year ago
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1 year ago
#2
(Original post by Mavs04)
Why is it not 25/16 here, isn’t 5/4 squared 25/16, not 25/8?
Because of the factor of 2 at the very beginning.

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#3
This is the way I did it in decimals and the answer turned out right, I’m not sure why the fraction is like that though
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#4
(Original post by Mavs04)
This is the way I did it in decimals and the answer turned out right, I’m not sure why the fraction is like that though
Would it not just be 2[(x +5/4)^2 - 25/16] +9 ???
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#5
(Original post by Mavs04)
Would it not just be 2[(x +5/4)^2 - 25/16] +9 ???
Wait I think I’ve got it:

= 2(x+5/4)^2-50/16 + 144/16
= 2(x+5/4)^2 + 94/16
= “””””””””””””” + 47/8

???
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1 year ago
#6
Okay, a few points:

POST 1:
As RDKGames has mentioned (in the second post of this discussion), (25/16) was multiplied by 2 to obtain (25/8):

POST 3:
Best to stick with fractional representation for this question as you may deal with non-ending decimal representations and it is clearer with fractions.

Also, on the third line of your script:

You have forgotten to square the (x + 1.25) term on this line and the lines afterwards.

POST 4:
Yes it is:

POST 5:
Yes but it is best to break down (50/16) to (25/8) so to be easier to malipulate the other terms.
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