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Homework Help: Calculus help derivatives

  1. Oct 20, 2004 #1
    i know this problem has to do with derivatives and i'm sure its easy, but for some reason i just can't figure it out...
    Find equations of both lines through the point (2,-3) that are tangent to the parabola y= x^2 + x

    help please...i know the derivative is 2x + 1 ....and that the 2 equations will be linear and pass through the point above, obviously...just not sure where to go from there. :blushing:
  2. jcsd
  3. Oct 20, 2004 #2
    This is differentiation, you have dy/dx =2x+1.then substitute the x=2 in the dy/dx,then you will find that dy/dx =5(that is the gradient of the tangent)

    y-(-3) =3(x-2)
    y+3 = 3x-6
    y= 3x-9 (equation of the tangent)

    The othe equation you mention may be the normal for the curve.Use formula

    m1 x m2 =-1

    then you can solve the question.
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