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Math Help - Another tangent and normal question

  1. #1
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    Another tangent and normal question

    If point A had co-ordinates (2,11) and I wanted to find the equation of the tangent of the curve of x + 3x + 1, and then the equation of the normal, would I do it like this?:

    dy/dx = 2x + 3

    Sub co-ordinate of x: 2
    Gradient of tangent = 7

    y-y1 = m(x-x1)
    y-11 = 7(x-2)
    y-11 = 7x-14
    y = 7x-3

    -----

    Gradient of normal [m1 x m2 = -1] 7 x -1 = -1/7


    y -11 / x - 2 = -1/7

    = 7y + x - 79 = 0
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  2. #2
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    Quote Originally Posted by db5vry View Post
    Gradient of normal [m1 x m2 = -1] 7 x -1 = -1/7

    y -11 / x - 2 = [U]-1/7
    Your answer is correct. You do have some minor mistakes or vague statements, but I assume they're just typos
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  3. #3
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    Tangent and Normal

    Looks fine to me!

    Grandad
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  4. #4
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    What even the last part is correct?!?!?!?!

    Thanks very much for taking the time to look at it.
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