Matematika

Pertanyaan

jika akar akar persamaan kuadrat 3x² + 5x + 1 = 0 adalah α dan β maka nilai[tex] \frac{1}{ \alpha ^{2} } + \frac{1}{ \beta ^{2} } [/tex] adalah

2 Jawaban

  • alpha = a
    betha = b

    3x² + 5x + 1 = 0
    a + b = -5/3
    ab = 1/3

    (1/a²) + (1/b²)
    = (a² + b²)/(ab)²
    = ((a + b)² - 2ab)/(ab)²
    = ((25/9) - (6/9))/(1/9)
    = 25 - 6
    = 19
  • Mapel : Matematika
    Kelas : X SMA
    Materi : Persamaan Kuadrat

    Pembahasan :
    3x² + 5x + 1 = 0

    Berdasarkan Teorema Vietta
    α + β = -b/a
    α + β = -5/3

    αβ = c/a
    αβ = 1/3

    Maka...
    1/α² + 1/β²
    = (α² + β²)/(α²β²)
    = [(α + β)² - 2αβ]/(αβ)²
    = [(-5/3)² - 2(1/3)]/(1/3)²
    = [25/9 - 2/3]/(1/9)
    = [19/9]/(1/9)
    = (19 x 9)/(1 x 9)
    = (19 x 1)/1
    = 19

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