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junior college 1 | H2 Maths
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junior college 1 chevron_right H2 Maths chevron_right Singapore

qs. 1 and 2 please, thank you in advance

Date Posted: 4 years ago
Views: 201
J
J
4 years ago
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)

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