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secondary 4 | A Maths
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Date Posted: 2 days ago
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hx² = 8 -> h = 8/x²
A = x² + 4hx = x² + 32/x
dA/dx = 2x - 32/x² = 0 -> x³ = 16 -> x = 2 ∛2
A = (2 ∛2)² + 32/(2 ∛2) = 4 ∛4 + 16/∛2 =12 ∛4 m²
d²A/dx² = 2 + 64/x³ > 0 when x is positive -> dA/dx is a minimum.
A = x² + 4hx = x² + 32/x
dA/dx = 2x - 32/x² = 0 -> x³ = 16 -> x = 2 ∛2
A = (2 ∛2)² + 32/(2 ∛2) = 4 ∛4 + 16/∛2 =12 ∛4 m²
d²A/dx² = 2 + 64/x³ > 0 when x is positive -> dA/dx is a minimum.
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