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find y in terms of x?

given that d^2y/dx^2=4 and when x=0 , y=2 and dy/dx=8, find y in terms of x

2 Answers

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  • cidyah
    Lv 7
    7 years ago

    d^2y /dx^2 = 4

    Integrate both sides

    dy/dx = 4x+C

    when x=0, dy/dx = 8

    8 = 4(0) + C

    C = 8

    dy/dx = 4x+8

    Integrate both sides

    y = 4 (x^2 /2) + 8x + C

    y = 2x^2 + 8x+ C

    when x=0, y=2

    2 = 2(0)^2 + 8(0) + C

    C = 2

    y = 2x^2 + 8x+ 2

  • y = ⌡⌡d^2y/dx^2 =⌡ dy/dx = ⌡⌡4 = ⌡4x + C = 2x^2 + Cx +K

    dy/dx|(x=0) = 8 = 0 + C ==> C = 8

    d^2y/dx^2|(x=0) = 2 = 0 + 0 + K ==> K = 2

    y = 2x^2 + 8x + 2

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