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Help - Q23 June 2011 - iGCSE

Hi,

I can't work this out at all - can somebody help me please?




Thanks in advance!
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Reply 1
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C0balt
16
Original post by ShivP_98
Hi,

I can't work this out at all - can somebody help me please?




Thanks in advance!


Express each of the numbers under the root in prime factors first

Posted from TSR Mobile
Reply 2
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ShivP_98
OP
11
Original post by C0balt
Express each of the numbers under the root in prime factors first

Posted from TSR Mobile


Okay so

sqrt(3 * 16) + sqrt(3 * 36)

Like that?

(edited 9 years ago)
squareroot = |

|(48) + |(108)

= |(3*16) + |(3*36)

= 4|(3) + 6|(3)

= 10|(3)
Reply 4
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ShivP_98
OP
11
It needs to be in the form k sqrt6 though not 3 :frown:
Reply 5
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ShivP_98
OP
11
Also if anyone has any time;



This one is hard for me too :frown:
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Well, you know that a∗b\sqrt{a*b} is equal to a∗b\sqrt a * \sqrt b.

You want each one in terms of 6\sqrt 6, so what do you do?

Edit: Sorry, this was the more direct root route but I missed that other people were helping with a different method.
(edited 9 years ago)
Reply 7
Avatar for ShivP_98
ShivP_98
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Try and make either a or b 6?
Original post by ShivP_98
It needs to be in the form k sqrt6 though not 3 :frown:




Strange question but you have 10root3

And 10 is 5 x root2 x root2
Original post by ShivP_98
Also if anyone has any time;



This one is hard for me too :frown:


I assume that you can square what you have

Then you need to adapt to make a^2 less than 10
Original post by sophie_emma96
x = a X 10^n

x^2 = (a X 10^n)^2

x^2 = (a X 10^n)(a X 10^n)

FOIL method:
x^2 = a^2 + a10^n + a10^n + 100^2n

x^2 = a^2 + 100^2n + 2(a X 10^n)


This is incorrect ... Can suggest that you either correct it or delete it
Original post by TenOfThem
This is incorrect ... Can suggest that you either correct it or delete it


I don't know how to correct it so I will delete it haha! Could you share the correct answer as I'm intrigued now! 😂
Original post by sophie_emma96
I don't know how to correct it so I will delete it haha! Could you share the correct answer as I'm intrigued now! 😂


You squared a+b instead of ab

(ab)^2 = a^2b^2
Original post by TenOfThem
You squared a+b instead of ab

(ab)^2 = a^2b^2


Oops stupid error there, clearly need to get to bed

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