Matematika

Pertanyaan

Tentukan rumus invers berikut ini:

a. f(x)= 3x - 2 : 4x + 7
b. f(x)= 5x - 10 : 3x + 4
c. f(x)= -2x + 5 : 4x - 7

1 Jawaban

  • a) f(x) = 3x - 2 / 4x + 7
    y = (3x - 2) / (4x + 7)
    y(4x + 7) = (3x - 2)
    4xy + 7y = 3x - 2
    4xy - 3x = -7y - 2
    x(4y - 3) = -7y - 2
    x = (-7y - 2) / (4y - 3)
    f-¹(x) = (-7x - 2) / (4x - 3)

    b) f(x) = 5x - 10 : 3x + 4
    cara 1 f-¹(x) = - 4x - 10 : 3x - 5

    cara 2 y = 5x - 10 : 3x + 4
    y (3x + 4) = 5x - 10
    3yx + 4y = 5x - 10
    3yx - 5x = - 4y - 10
    x (3y - 5) = -4y - 10
    x = (-4y - 10) : (3y - 5)
    f-¹(x) = - 4x - 10 : 3x - 5

    c) f(x) = -2x + 5 : 4x - 7
    f-¹(x) = 7x + 5 : 4x + 2

    cara yang paling mudah
    f(x) = ax + b : cx + d
    f-¹(x) = -dx + b : cx - a

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