C1 question (completing the square or quadratic formula)

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WilliamSlim
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Hello my good friends, i aced this question (or so i thought) and was proper chuffed, until i looked at the mark scheme.

http://www.examsolutions.net/a-level...June/paper.php

Q11

I got to the value it wnated through using completing the suare and not formula, but the mark scheme makes no mention of using completing the square and only using the formula. So would i still get the marks if i did it using compelting the square?
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lizard54142
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(Original post by WilliamSlim)
Hello my good friends, i aced this question (or so i thought) and was proper chuffed, until i looked at the mark scheme.

http://www.examsolutions.net/a-level...June/paper.php

Q11

I got to the value it wnated through using completing the suare and not formula, but the mark scheme makes no mention of using completing the square and only using the formula. So would i still get the marks if i did it using compelting the square?
A valid method used to reach the correct answer will always receive full marks.
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brianeverit
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(Original post by WilliamSlim)
Hello my good friends, i aced this question (or so i thought) and was proper chuffed, until i looked at the mark scheme.

http://www.examsolutions.net/a-level...June/paper.php

Q11

I got to the value it wnated through using completing the suare and not formula, but the mark scheme makes no mention of using completing the square and only using the formula. So would i still get the marks if i did it using compelting the square?
Surely the mark scheme says "by formula or completing the square" so what are you worried about?
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WilliamSlim
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(Original post by brianeverit)
Surely the mark scheme says "by formula or completing the square" so what are you worried about?
I don't see anything about completing the square on the mark scheme, i'm not so good at words and letters stuff so maybe you lads could take a look?
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lizard54142
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(Original post by WilliamSlim)
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I don't see anything about completing the square on the mark scheme, i'm not so good at words and letters stuff so maybe you lads could take a look?
Which part question are you talking about, a b or c? Show us your working out.
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lizard54142
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Did you even read the mark scheme?
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gdunne42
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(Original post by WilliamSlim)
Hello my good friends, i aced this question (or so i thought) and was proper chuffed, until i looked at the mark scheme.

http://www.examsolutions.net/a-level...June/paper.php

Q11

I got to the value it wnated through using completing the suare and not formula, but the mark scheme makes no mention of using completing the square and only using the formula. So would i still get the marks if i did it using compelting the square?
Firstly, completing the square or using the formula are really the same thing and are equally valid ways to solve the problem.You can always use any mathematically valid method to solve a question unless the question states otherwise.
I prefer completing the square on C1 because your surd solution will be in the simplest form where the formula result will often need simplification.



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