Matematika

Pertanyaan

jika a dan b adalah akar persamaan kuadrat x^2-3x-1 maka a^4+6a^2b^2+b^4=

2 Jawaban

  • x² - 3x - 1 ; diperoleh p = 1, q = -3, r =-1

    a + b= -q/p = -(-3)/1 = 3
    a.b = c/p = -1/1 = -1

    a⁴ + 6a²b² + b⁴
    = (a + b)⁴ - 4a³b - 4ab³
    = (a + b)⁴ - 4ab(a² + b²)
    = (a + b)⁴ - 4ab((a + b)² - 2ab)
    = (3)⁴ - 4(-1)((3)² - 2(-1))  
    = 81 + 4(9 + 2)
    = 81 + 44
    = 125

    cmiiw
  • x^2 - 3x - 1 = 0
    a + b = -(-3)/1 = 3
    ab = -1/1 = -1

    a^2 + b^2 = (a + b)^2 - 2ab = (3)^2 - 2(-1) = 9 + 2 = 11

    a^4 + 6a^2b^2 + b^4
    = a^4 + 2a^2b^2 + b^4 + 4a^2b^2
    = (a^2 + b^2)^2 + 4(ab)^2
    = (11)^2 + 4(-1)^2
    = 121 + 4
    = 125

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