Where have I gone wrong here? (GCSE Maths) Watch

BigBaba
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Good evening everyone,

I am learning about Surds on MyMaths and I am not sure how to work out these two questions, can someone please help me?

(I have tried putting the same answer with my Wi-Fi on - Superhub restarted itself lol)

Name:  Screenshot 2013-11-20 19.35.50.png
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Can someone please show me how to work it out?
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Super199
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I'm guessing you know how to expand double brackets? Have you been taught how to simplify surd?. Show your workings and I'll try and see what you're doing wrong.
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BigBaba
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(Original post by Super199)
I'm guessing you know how to expand double brackets? Have you been taught how to simplify surd?. Show your workings and I'll try and see what you're doing wrong.
Hello!

I did the rainbow method, below are my working outs:

Q2.

√5√5 + 7√5-5√5-35
√5x5 = 5 and +7√5-5√5 = 2√5
-35+5 = -30

Just to give you an idea, I used the same rainbow method for Q3, can you help me work it out please?
(I hope you understand my working out, it is harder to do on PC :/)
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Kvothe the Arcane
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(Original post by BigBaba)
Hello!

I did the rainbow method, below are my working outs:

Q2.

√5√5 + 7√5-5√5-35
√5x5 = 5 and +7√5-5√5 = 2√5
-35+5 = -30

Just to give you an idea, I used the same rainbow method for Q3, can you help me work it out please?
(I hope you understand my working out, it is harder to do on PC :/)
I'm not sure what this rainbow method is.
BUt you want to evaluate (6+ \sqrt{7})(3- \sqrt{7}) \equiv 6(3- \sqrt{7})+\sqrt{7}(3- \sqrt{7}). Does that help?
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BigBaba
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(Original post by keromedic)
I'm not sure what this rainbow method is.
BUt you want to evaluate (6+ \sqrt{7})(3- \sqrt{7}) \equiv 6(3- \sqrt{7})+\sqrt{7}(3- \sqrt{7}). Does that help?
Hello!

Yes, that is basically what I did, by rainbow I mean a curved line from first term in bracket one to first time in bracket two, and then the same for the second term/ figure in the brackets

Edit

Wait, I think it's called the FOIL method, not rainbow hahah!
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uberteknik
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(Original post by BigBaba)
Good evening everyone,

I am learning about Surds on MyMaths and I am not sure how to work out these two questions, can someone please help me?

(I have tried putting the same answer with my Wi-Fi on - Superhub restarted itself lol)

Name:  Screenshot 2013-11-20 19.35.50.png
Views: 168
Size:  297.8 KB

Can someone please show me how to work it out?
You have not done anything wrong. Q2 correct as far as I can see.

For Q3 however, it's normal to put the positive term first because it's less likely you will miss the minus sign when doing longer calculations

the answer becomes: 11-3sqrt7

For Q4. This is known as a conjugate and the answer will be an integer.
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brianeverit
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(Original post by BigBaba)
Good evening everyone,

I am learning about Surds on MyMaths and I am not sure how to work out these two questions, can someone please help me?

(I have tried putting the same answer with my Wi-Fi on - Superhub restarted itself lol)

Name:  Screenshot 2013-11-20 19.35.50.png
Views: 168
Size:  297.8 KB

Can someone please show me how to work it out?
I think your answers are correct.!
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