Matematika

Pertanyaan

Persamaan kuadrat x^2-3x-4=0 mempunyai akar x1 dan x2 .(x1/x2-1) dan (x2/x1-1) adalah..
A. 4x^2+9x-9=0
B. 4x^2+17x-17=0
C. 4x^2+-17x+17=0
D. 4x^2+25x+25=0
E. 4x^2-25x+25=0
Tolong jawab yaa.....

1 Jawaban

  • x^2 - 3x - 4 = 0
    x1 + x2 = -b/a = -(-3)/1 = 3
    x1.x2 = c/a = -4/1 = -4
    (x1)^2 + (x2)^2 = (x1 + x2)^2 - 2x1.x2 = (3)^2 - 2(-4) = 9 + 8 = 17
    x1/x2 + x2/x1 = (x1^2 + x2^2)/(x1.x2) = 17/-4

    Misal p = x1/x2 - 1 dan q = x2/x1 - 1
    p + q = (x1/x2 - 1) + (x2/x1 - 1) = x1/x2 + x2/x1 - 2 = -17/4 - 2 = -25/4
    p.q = (x1/x2 - 1)(x2/x1 - 1) = 1 - (x1/x2 + x2/x1) + 1 = 1 - (-17/4) + 1 = 25/4
    Persamaan kuadrat baru
    x^2 - (p + q)x + pq = 0
    x^2 - (-25/4)x + 25/4 = 0 ======> kali 4
    4x^2 + 25x + 25 = 0

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