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Yih
Yih

Secondary 4 chevron_right A Maths chevron_right Malaysia

Please help. Thank you

Date Posted: 8 months ago
Views: 56
J
J
8 months ago
Use quadratic formula to find each root first.


α is the one with the + sign.

Find the cube of it and rewrite the right hand side in terms of α
Eric Nicholas K
Eric Nicholas K
8 months ago
There are many ways to do this question. Resubstitution into original equation works. I will demonstrate one later if I have time.
Eric Nicholas K
Eric Nicholas K
8 months ago
One way (and in fact, the easiest) is to factorise the terms in x by taking out x and then multiply both sides by the 'conjugate' of 2a - 3 i.e. 2a + 3.

2a2 - 3a = 7
a (2a - 3) = 7
a (2a - 3) (2a + 3) = 7 (2a + 3)
a (4a2 - 9) = 14a + 21
4a3 - 9a = 14a + 21
4a3 = 23a + 21
Yih
Yih
8 months ago
Thank you!

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Eric Nicholas K
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