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calculate gradient of curve - need help

  • 26-10-2008 11:52am
    #1
    B1977
    Registered Users, Registered Users 2 Posts: 410 ✭✭


    y= 3x squared +2x+7=0 at the point where x = -2


Comments

  • #2
    professore
    Closed Accounts Posts: 5,857 ✭✭✭professore


    B1977 wrote: »
    y= 3x squared +2x+7=0 at the point where x = -2

    differentiate it wrt x and plug in -2. BTW y = mx + c won't work since that's the equation of a line not a curve.

    So dy/dx = 6x + 2 (I think ... years since i've done it).

    => 6 * -2 + 2

    = -10

    y = x^n

    dy /dx = nx^n-1

    Sorry, think it might be x + 2 .... I can't find any examples on the web for something this simple ... check your maths book

    In general to get the gradient (or slope) of a curve at any point just get the derivative and plug in the number.


  • #3
    B1977
    Registered Users, Registered Users 2 Posts: 410 ✭✭B1977


    it says in question,without drawing graph


  • #4
    B1977
    Registered Users, Registered Users 2 Posts: 410 ✭✭B1977


    i am really looking for the formula to use.can i use y =mx+c
    i know its simple I just cant find the right wy to do it,

    thanks for replying


  • #5
    Fremen
    Registered Users, Registered Users 2 Posts: 2,481 ✭✭✭Fremen


    Y = mx + c will NOT work, that only applies to straight lines.

    As professore said, take the derivative and plug in -2 in place of X.


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