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A bit of help appreciated.. watch

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    Don't really know what to do here :

    "At a particular point of the curve y = 5x^2 - 12x + 1 the equation of the normal is x + 18y + c = 0. Find the value of constant c."

    I know that 'cos the gradient of the normal is 1, the gradient of the tangent is -1, but that's it really.

    Any advice/help appreciated.

    Thanks
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    Nope, the gradient of the normal isn't 1. Get the equation in the form y = mx + b and you'll see what the gradient of the normal is.
    Once you've done that:
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    Differentiate y = 5x^2 - 12x + 1 and set dy/dx equal to the gradient of the tangent. You'll have x. You can get y, so you can find c.
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    Yeah thanks, I realised that just after I posted. Sorry!

    Thanks a lot.
 
 
 
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