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junior college 1 | H2 Maths
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qs. 1 and 2 please, thank you in advance
Date Posted: 4 years ago
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2lg(x) - lg(x + 20) = 1
lg(x²) - lg(x + 20) = 1
lg( x²/(x + 20) ) = 1
x²/(x + 20) = 10¹ = 10
x² = 10x + 200
x² - 10x - 200 = 0
(x + 10)(x - 20) = 0
x = -10 or x = 20
(n.a, x cannot be negative as lg(x) is undefined for x ≤ 0)
lg(x²) - lg(x + 20) = 1
lg( x²/(x + 20) ) = 1
x²/(x + 20) = 10¹ = 10
x² = 10x + 200
x² - 10x - 200 = 0
(x + 10)(x - 20) = 0
x = -10 or x = 20
(n.a, x cannot be negative as lg(x) is undefined for x ≤ 0)
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