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secondary 4 | A Maths
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Date Posted: 4 years ago
Views: 212
Later if no one does this
The ans can also be 0. There are 2 ans for the y value.
(3^y)^2 - 10 (3^y) + 9 = 0
You can use a substitution u = 3^y if you are scared of factorising the equation straight away
u^2 - 10u + 9 = 0
(u - 9) (u - 1) = 0
u = 9, u = 1
But u = 3^y
3^y = 9, 3^y = 1
3^y = 3^2, 3^y = 3^0
Comparing powers, y = 2 or y = 0
You can use a substitution u = 3^y if you are scared of factorising the equation straight away
u^2 - 10u + 9 = 0
(u - 9) (u - 1) = 0
u = 9, u = 1
But u = 3^y
3^y = 9, 3^y = 1
3^y = 3^2, 3^y = 3^0
Comparing powers, y = 2 or y = 0
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Date Posted:
4 years ago
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