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Quadratic Equation - C3

How would you solve this 16x2−12x−1=016x^{2}-12x-1=0 ok, this is the last part of a question on functions, I can finish the question by just putting the equation into my calculator and I get the correct answers. However I will have no method marks, so how would you solve this without using a calculator directly?? thanks to anyone who helps :smile:

I can do it now, mind went blank and forgot about the quadratic formula, and I'm supposed to get an A*....
(edited 12 years ago)
Reply 1
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tdx
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you can't factorise and I tried completing the square but got VERY confused!
Reply 2
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Dr A
Original post by tdx
you can't factorise and I tried completing the square but got VERY confused!


Use the formula.

x=−b±b2−4ac2a\displaystyle x=\frac{-b\pm \sqrt{b^2 -4ac}}{2a}

put the values in and simplify to get exact solutions.
(edited 12 years ago)
Reply 3
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tdx
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no worries, I can do it now (I hope) I forgot you could use the quadratic equation... :/ silly me, haha :')
Reply 4
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tdx
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Original post by Dr A
Use the formula.


cheers :smile: just realised that a second ago, hitting myself now
Quadratic formula?
Reply 6
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z0tx
12
Unparseable latex formula:

\begin{array}{*{20}c} {x = \frac{{ - b \pm \sqrt {b^2 - 4ac} }}{{2a}}}



... should be a reflex by the way.
(edited 12 years ago)
Reply 7
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tdx
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Original post by z0tx
Unparseable latex formula:

\begin{array}{*{20}c} {x = \frac{{ - b \pm \sqrt {b^2 - 4ac} }}{{2a}}}



... should be a reflex by the way.


what's a reflex? :/
Original post by tdx
what's a reflex? :/


i.e. that's one of the first things you should think of when you first see a quadratic :wink:
factorising, completing the square and the formula will eventually get you the X value
Reply 10
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tdx
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Original post by thegodofgod
i.e. that's one of the first things you should think of when you first see a quadratic :wink:


haha yeah, mind went blank for a minute :') lol

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