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secondary 4 | A Maths
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Kathy
Kathy

secondary 4 chevron_right A Maths chevron_right Singapore

thank you

Date Posted: 7 months ago
Views: 42

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Mathaddict100
Mathaddict100's answer
348 answers (A Helpful Person)
1st
These are the solutions needed for you to answer qn 12..I'll come back to show you the answer for the following qn in a while..
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Mathaddict100
Mathaddict100's answer
348 answers (A Helpful Person)
I hope this is correct..I can only think of 'complete the square' method besides factorisation and I can see that it is quite possible to do so..
Wong Keng Choon
Wong Keng Choon
7 months ago
Hi, Mathaddict100, I respectfully disagree with your answer for Q13, because you have to take the expansion of (1-1/(2x))^2 into account.
Also, the 'hence' part means you have to use your expansion of (1+x+x2)^10 in solving the 2nd part. See my answer below for details.
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Wong Keng Choon
Wong Keng Choon's answer
40 answers (Tutor Details)
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Mathaddict100
Mathaddict100
7 months ago
Thank you sir for pointing out my mistake.I understood where I went wrong.Appreciate it.I did put the other expression into account but my first expansion itself is wrong.So,it ultimately become wrong for the last part.Would you mind explaining why is completing the square method invalid while the latter should? I seriously do want to know..Thanks :)
Wong Keng Choon
Wong Keng Choon
7 months ago
Hi, your completed square is wrong. The completed square for x^2+x+1 should be (x+1/2)^2 + 3/4. Also, if you use completing the square method, it would be more tedious expanding (1+x+x^2)^10 because you cannot use the shorter method of expanding (1+b)^n to expand ((x+1/2)^2 + 3/4)^10.
Mathaddict100
Mathaddict100
7 months ago
Oh that's how it is.Yup I agree on the tediousness part.Great thanks for the explanation. :)