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secondary 4 | A Maths
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Polytechnic math qn: How to do part c? I have problems when it comes to showing this showing that, prove this prove that. Please help!
Here is one way you can do this :
log₄y = p
log₂ y / log₂ 4 = p (Change of base)
log₂ y / log₂ 2² = p
log₂ y / 2log₂ 2 = p (bring down the power)
log₂ y / 2 = p
log₂ y = 2p ①
Next,
log₈2y = q
log₈ 2 + log₈ y = q (Addition of logs)
log₈ 8¹/³ + log₂ y / log₂ 8 = q (Change of base)
⅓ log₈ 8 + log₂ y / log₂ 2³ = q
⅓ + log₂ y / 3log₂ 2 = q (bring down the power)
⅓ + log₂ y / 3 = q
1 + log₂ y = 3q ②
Sub ① into ②,
1 + 2p = 3q
2p = 3q - 1
log₄y = p
y = 4ᵖ
y = (2²)ᵖ
y = 2²ᵖ ①
Next,
log₈ 2y = q
2y = 8ᑫ
2y = (2³)ᑫ
2y = 2³ᑫ
y = 2³ᑫ / 2
y = 2³ᑫ⁻¹ ②
① = ②
2²ᵖ = 2³ᑫ⁻¹
Since they are both single terms and they have identical bases, their powers are equal.
2p = 3q - 1
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