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Find the equation of the line...?

Find the equation of the line which goes through (0,4) & is perpendicular to the line: l(t) = <3+5t, 2-3t>

Please give the details and steps!!

Thank you

Update:

Thank you all, I understand this concept much better, and it's actually easy now!!

2 Answers

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  • 9 years ago
    Favorite Answer

    You can eliminate the parameter t, and then find the equation.

    x=3+5t

    y=2-3t

    Multiply the first equation by 3 and the second one by 5, and then add the resulting equations

    3x = 9 + 15 t

    5y = 10 - 15 t

    ----------------------

    3x+5y = 19

    5y = -3x +19

    y = (-3/5)x + 19/5

    The slope of this line is -3/5. So the slope of the line you are looking for is 5/3. And you know that the line passes through (0,4), so its equation is given by

    y-4 = (5/3)(x-0)

    y-4 = (5/3)x

    y = (5/3)x + 4

  • 9 years ago

    We can use the vector function to write parametric equations for our line.

    x=3+5t

    y=2-3t

    I now solve 1 of these equations for t and plug it into the other equation

    x=3+5t

    x-3=5t

    (x-3)/5=t

    y=2-3(x-3)/5

    y=2-3/5x-9/5

    y=1/5-3/5x

    This line has a slope of -3/5. Any line prepindicular to it must have a slope of 5/3. I use this information and the point given to find the equation of the prepindicular line, (I will use L(x) to represent the prepindicular line)

    L(x)-4=5/3(x-0)

    L(x)=5/3x+4

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