Toán Lớp 9: Giải phương trình
√(4x^2 + 4x + 1) – x = 5
√(x^2-1) – 2√(x+1) = 0
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Toán Lớp 9: Giải phương trình
√(4x^2 + 4x + 1) – x = 5
√(x^2-1) – 2√(x+1) = 0
Comments ( 2 )
a)
(=) √(2x + 1)² = 5 – x (x ≤ 5)
(=) |2x + 1| = 5 – x
(=) 2x + 1 = 5 – x hoặc 2x + 1 = x – 5
(=) 3x = 4 hoặc x = – 6
(=) x = 4/3 (nhận) hoặc x = – 6 (nhận)
b)
(=) √(x² – 1) = 2√(x + 1) (x ≥ 1)
(=) √(x + 1) = √(x² – 1)/2
(=) x + 1 = (x² – 1)/4
(=) 4x + 4 = x² – 1
(=) x² – 4x – 5 = 0
(=) x² + x – 5x – 5 = 0
(=) x(x + 1) – 5(x + 1) = 0
(=) (x + 1)(x – 5) = 0
(=) x = – 1 (loại) hoặc x = 5 (nhận)