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secondary 4 | A Maths
2 Answers Below
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Date Posted: 4 years ago
Views: 260
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You must understand the laws or rules of logarithm. Read them first together with the laws of indices.
Then slowly follow thro my steps. You need more practices on this topic.
Then slowly follow thro my steps. You need more practices on this topic.
Date Posted:
4 years ago
There's an error in the 3rd last line.
ln(y/x²) - ln2 = 0
ln(y/x² ÷ 2) = ln(y/x² × ½) = 0
ln(y/(2x²)) = 0 = ln 1
y/(2x²) = 1
y = 2x²
(y/x²)/2 instead of y/(x²/2)
ln(y/x² ÷ 2) = ln(y/x² × ½) = 0
ln(y/(2x²)) = 0 = ln 1
y/(2x²) = 1
y = 2x²
(y/x²)/2 instead of y/(x²/2)
Alternative answer :
lny = 2lnx + c
lny = lnx² + c
e^(lny) = e^(lnx² + c) = e^(lnx²) (e^c)
y = (e^c) x²
Sub y = 18, x = 3
18 = (e^c)(3²)
18 = 9e^c
e^c = 2
So y = 2x²
lny = 2lnx + c
lny = lnx² + c
e^(lny) = e^(lnx² + c) = e^(lnx²) (e^c)
y = (e^c) x²
Sub y = 18, x = 3
18 = (e^c)(3²)
18 = 9e^c
e^c = 2
So y = 2x²
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