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If the function f:R->R satisfies f(2x-1)=5x+2, find f^(-1) (3x+1)?

given answer: (6x-7) /5

3 Answers

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  • mizoo
    Lv 7
    2 years ago
    Favorite Answer

    2x - 1 = a => x = (1/2)(a + 1)

    f(a) = 5x + 2

    f(a) = 5((1/2)(a + 1)) + 2

    f(a) = (5/2)a + 9/2

    f(x) = (5/2)x + 9/2

    f^(-1)(x) :

    y = (5/2)x + 9/2

    y - 9/2 = 5/2 * x

    x = 2/5 * (y - 9/2)

    f^-1(x) = 2/5 * (x - 9/2)

    f^-1(3x + 1) = 2/5 * ((3x + 1) - 9/2)

    f^-1(3x + 1) = 6/5 x + 2/5 - 9/5

    f^-1(3x + 1) = (6x - 7)/5

  • ?
    Lv 7
    2 years ago

    We first get f(x)

    Since f(2x-1) = 5x+2

    set u = 2x-1 or x = (u+1)/2

    and we have f(u) = 5(u+1)/2 + 2 = (5u+ 9)/2

    or y = (5u+9)/2

    to find the inverse we switch y and u

    u = (5y+9)/2

    y = ( 2u-9)/5

    or f^-1(u) = (2u-9/5

    So f^-1(3x+1) = ( 2 (3x+1) - 9)/5 = ( 6x-7)/5

  • 2 years ago

    Well since (5/2)(2x-1) + 9/2 = 5x+2, then f(x) = (5/2)x + 9/2

    and f^-1(x) = (2x-9)/5

    So f^-1(3x+1) = (2(3x+1)-9)/5 = (6x-7)/5

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