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Pertanyaan

lim (x-> 2) √(ax+b)-3/(x^2-4)=1/4 maka nilai a+b=

1 Jawaban

  • Gunakan L'hospital dan ingat jika : y = √f(x) maka y' = f'(x)/2√f(x)

    Lim (√(ax + b) - 3)/(x^2 - 4) = 0/0 jika x = 2
    (√(a(2) + b) - 3)/(2^2 - 4) = 0/0
    √(2a + b) - 3 = 0
    √(2a + b) = 3

    Lim (√(ax + b) - 3)/(x^2 - 4) = 1/4 jika sesudah diturunkan
    x=>2

    Lim [a/(2√(ax + b))] / 2x = 1/4
    x=>2

    [a/(2√(a(2) + b))] / 2(2) = 1/4
    [a/2√(2a + b)] / 4 = 1/4
    a/2√(2a + b) = 1
    a/2(3) = 1
    a = 6

    √(2a + b) = 3
    2a + b = 9
    2(6) + b = 9
    b = -3

    a + b = 6 + (-3) = 3

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