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Math Help - Find the tangent.

  1. #1
    Member classicstrings's Avatar
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    Find the tangent.

    How would i find the tangent to the quadratic 2x^2 -12x + 14 at the point (1,4)? Do we take the derivative of the equation? Thanks
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  2. #2
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    yes, that's right, you need to differentiate it.
    let
    f(x) = 2x^2-12x+14
    when x = 1
    f(x) = 2-12+14 = 4
    so the point (1,4) does lie on the curve.
    f'(x) = 4x-12
    f'(1) = 4-12 = -8
    so the gradient of the curve at (1,4) is -8.
    you could also find the equation of the tangent line that touches the curve at (1,4) but i don't think that's what you need to do.
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  3. #3
    Member classicstrings's Avatar
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    Yeah the equation is y = -8x + 12 after simple substitution. Thanks!
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