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secondary 4 | A Maths
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Kathy
Kathy

secondary 4 chevron_right A Maths chevron_right Singapore

any easy way to do this?
Thank you

Date Posted: 2 months ago
Views: 23

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Eric Nicholas K
Eric Nicholas K's answer
1640 answers (Tutor Details)
1st
Here is my working for part (a). I use substitution of several values of x to find the values of A, B and C. There is another way called comparing coefficients, but this is more effective only in certain situations.
Kathy
Kathy
2 months ago
Can you show me the comparing coefficient
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Eric Nicholas K
Eric Nicholas K's answer
1640 answers (Tutor Details)
Here is my working for part (b). I used a mix of substitution of x and comparison of coefficients to find the values of A, B and C.
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Eric Nicholas K
Eric Nicholas K's answer
1640 answers (Tutor Details)
Here is my working for part (c). Alas, there is no hard and fast rule on which method is the easiest. I will now do part (iv), and once done, I will show you how to compare coefficients for part (i).
Eric Nicholas K
Eric Nicholas K
2 months ago
Setting x = 0 instead of x = 1 at the start may have been a slightly better choice.
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Eric Nicholas K
Eric Nicholas K's answer
1640 answers (Tutor Details)
Here is my working for part (d). Again, the choices are highly dependent on whether there are any nice bracketed terms at the start or not and also where the unknowns are placed.

Actually, instead of setting x = 4, setting x = 0 (achieves the same effect as comparing constants) might be slightly more appealing, since anything attached to x will vanish.
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Eric Nicholas K
Eric Nicholas K's answer
1640 answers (Tutor Details)
Here is my approach for part (a) using comparing coefficients method.

Fortunately, I obtain A from the comparison of x2 immediately.

In the most unfortunate situation, you may have three simultaneous equations with three unknowns, which can get very long (or rather, draggy) to solve.