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# C1 question? watch

1. Spoiler:
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can anyone help me with question number four?
I've factorised it (probabley wrong) to 16x^2 - 144x + 99 and now... I don't know what else to do?

thanks for any help

(question in spoiler)
2. put it into 2 brackets? I cant see it for this one so i would use the formula, if you remember it
3. (minus b plus or minus the square root of b squared minus four times a times c) divided by 2 times a.
4. (Original post by GeorgieBoy)
(minus b plus or minus the square root of b squared minus four times a times c) divided by 2 times a.
could you factorise this without the formula? put it straight into brackets. I have trouble 'seeing' how it works with these large numbers.... no cheating :L
5. If you don't want to use the formula I guess you could do it by completing the square. Have you learnt that? Or if you want to put it straight into brackets, then you need to multiply 16x^2 by 99. This will give you an answers of 1584x^2. And from there you would need to find to number which multiply to give that, and two which add to give 144x. Sorry for the **** explantion.
6. (Original post by GeorgieBoy)
If you don't want to use the formula I guess you could do it by completing the square. Have you learnt that? Or if you want to put it straight into brackets, then you need to multiply 16x^2 by 99. This will give you an answers of 1584x^2. And from there you would need to find to number which multiply to give that, and two which add to give 144x. Sorry for the **** explantion.
ah right thankyou
7. Hi. First part of the question is to derive that equation. To do this, you need to use the volume of 495 and the usual basexheightxlength formula, but this one's a little more complicated seeing as there's a huge block cut out of the middle lol.

So the formula I got for the volume was 10x8x20-(10-2x)(8-2x)(20)=495
Expanding everything out gives you 1600-1600+720x-80x^2=495
Cancelling the 1600's and dividing through by 5 gives 144x-16x^2=99
Rearranging gives the formula required in the question.

For the second part, this equation factorises to (4x-33)(4x-3)=0 I got lucky and saw it right off... Looks like I've been doing too much Maths :O lol anyway carrying on.

So the answers you get are x=33/4 or x=3/4. Hope this helps

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Updated: September 28, 2010
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