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Math Help - equation of the normal of the line on point..

  1. #1
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    equation of the normal of the line on point..

    find the equation of the line (3, -5) and (-1,2)

    i did it and got an equation y = -7/4x + 1/4

    how its asking to find the equation of the normal of this line at point (3, -5)

    how do i get that?

    i know u use m1 and m2, u have y = m2x + b.. how do u work out b?

    m2 = 4/7 and x = 3 but b ?

    thank u!!
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  2. #2
    Rhymes with Orange Chris L T521's Avatar
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    Quote Originally Posted by jvignacio View Post
    find the equation of the line (3, -5) and (-1,2)

    i did it and got an equation y = -7/4x + 1/4

    how its asking to find the equation of the normal of this line at point (3, -5)

    how do i get that?

    i know u use m1 and m2, u have y = m2x + b.. how do u work out b?

    m2 = 4/7 and x = 3 but b ?

    thank u!!
    Since the equation of the normal line is y=\tfrac{4}{7}x+b, to find b, plug in the point (3,-5).

    This tells us that -5=\tfrac{4}{7}(3)+b\implies b=\dots

    Take it from here.

    --Chris
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  3. #3
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    Quote Originally Posted by Chris L T521 View Post
    Since the equation of the normal line is y=\tfrac{4}{7}x+b, to find b, plug in the point (3,-5).

    This tells us that -5=\tfrac{4}{7}(3)+b\implies b=\dots

    Take it from here.

    --Chris
    ohh damnit lol why didnt i think of that. make b the subject
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