GCSE Maths question Quadratics Please help!

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Daisiee
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Completing the square to (ax + b)^2 + c

4x^2 + 8x + 5 becomes in the a(x + b)^2 + c form as:
4(x +1)^2 + 1

But it is asking it to be in the form (ax +b)^2 + c:
How do I change it to that form??
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mqb2766
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(Original post by Daisiee)
Completing the square to (ax + b)^2 + c

4x^2 + 8x + 5 becomes in the a(x + b)^2 + c form as:
4(x +1)^2 + 1

But it is asking it to be in the form (ax +b)^2 + c:
How do I change it to that form??
4 is 2^2, so how can you take that inside the squared brackets. Just expand what you think to verify.

Or long winded, you could expand (ax +b)^2 and compare the quadratic and linear terms with the oriignal quadratic expression to get a and b.
Last edited by mqb2766; 4 days ago
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Daisiee
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(Original post by mqb2766)
4 is 2^2, so how can you take that inside the squared brackets. Just expand what you think to verify.

Or long winded, you could expand (ax +b)^2 and compare the quadratic and linear terms with the oriignal quadratic expression to get a and b.
Oh thank you. So I should kind of play with the numbers when I'm asked to put in that form? There is no specific formula to follow or anything?
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mqb2766
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(Original post by Daisiee)
Oh thank you. So I should kind of play with the numbers when I'm asked to put in that form? There is no specific formula to follow or anything?
If you do the first hint using 4 = 2^2, the formula should be obvious? The second way of expanding (ax+b)^2 and comparing terms is a fall back way to do it.

Post what you got and I'll explain a bit more if necessary.
Last edited by mqb2766; 4 days ago
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Daisiee
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(Original post by mqb2766)
If you do the first hint using 4 = 2^2, the formula should be obvious? The second way of expanding (ax+b)^2 and comparing terms is a fall back way to do it.

Post what you got and I'll explain a bit more if necessary.
I understood it. Thanks!
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