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secondary 2 | Maths
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secondary 2 chevron_right Maths chevron_right Singapore

Not sure how to do this

Date Posted: 6 days ago
Views: 16
snell
Snell
6 days ago
srly ? ? ?



lol



y² = 3 or y² = 1

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J
J
6 days ago
y⁴ - 4y² + 3 = 0

now notice that y⁴ = (y²)²

So

(y²)² - 4(y²) + 3 = 0

It is actually now in the form of a quadratic equation. You can use a substitution like u = y² if you find it difficult to visualise.

Then,

(y² - 1)(y² - 3) = 0

y² - 1 = 0 or y² - 3 = 0

y² = 1 or y² = 3

y = ± 1 or y = ± 3 (rejected as y is integer)


So y = 1 or y = -1
Eric Nicholas K
Eric Nicholas K
6 days ago
Probably the quadratic idea does not appear to be “automatic” for Sec 2 students since they think of quadratic as ax2 + bx + c = 0 and not other forms like ax4 + bx2 + c = 0 or ax6 + bx3 + c = 0.
Nalin Sharma
Nalin Sharma
6 days ago
No this is correct, my bad.
J
J
6 days ago
Not automatic for most at upper levels too. This question is probably meant to broaden their horizons, and might come out in exams as a way to test them/differentiate between A1s and A2s

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Eric Nicholas K
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