Matematika

Pertanyaan

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2 Jawaban

  • Mapel : Matematika
    Tingkat : Olimpiade
    Materi : Pecahan

    Pembahasan :
    Misal
    x = 1 + 1/[2 + (1/x)]
    x = 1 + 1/[(2x + 1)/x]
    x = 1 + x/(2x + 1)
    x = (2x + 1)/(2x + 1) + x/(2x + 1)
    x = (3x + 1)/(2x + 1)
    2x² + x = 3x + 1
    2x² - 2x - 1 = 0

    Pakai Rumus ABC, ambil yg positif
    X = (1 + √3)/2
    X = 1/2 (1 + √3)

    Opsi B.
  • Misal
    1 + 1/(2 + 1/(1 + 1/(2 + 1/(1 + 1/(2 + ..))))) = x
    1 + 1/(2 + 1/x) = x
    1 + 1/((2x + 1)/x) = x
    1 + x/(2x + 1) = x
    x/(2x + 1) = x - 1
    x = (2x + 1)(x - 1)
    x = 2x^2 - x - 1
    2x^2 - 2x - 1 = 0 ===> bagi 2
    x^2 - x - 1/2 = 0
    x^2 - x = 1/2 ===> kedua ruas ditambah 1/4
    x^2 - x + 1/4 = 1/2 + 1/4
    (x - 1/2)^2 = 3/4
    x - 1/2 = ± √(3/4)
    x = 1/2 ± √3 / 2
    x = 1/2 (1 ± √3)
    x = 1/2 (1 + √3) atau x = 1/2 (1 - √3)