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Math Help - Line equation : general understanding (Need ASAP help , exam tomorow)

  1. #1
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    Exclamation Line equation : general understanding (Need ASAP help , exam tomorow)

    Hello everyone ,

    This is my first time here and because i dont have a lot of time left due of my examination tomorrow i will not spend much time on the grammar.

    The point A has coordinates (7,7) and the line L has equation x+3y=8

    (i) Find the equation of the line that passes through A and is perpendicular to L

    I cant understand generaly what am i supposed to do here , plz provide me step by step with no "wordy" words , as simple as possible
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  2. #2
    Super Member Quacky's Avatar
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    Quote Originally Posted by Sumaher4 View Post
    Hello everyone ,

    This is my first time here and because i dont have a lot of time left due of my examination tomorrow i will not spend much time on the grammar.

    The point A has coordinates (7,7) and the line L has equation x+3y=8

    (i) Find the equation of the line that passes through A and is perpendicular to L

    I cant understand generaly what am i supposed to do here , plz provide me step by step with no "wordy" words , as simple as possible
    Start by rewriting your equation in y=mx+c form:

    3y=-x+8
    y=\frac{-1}{3}x+\frac{8}{3}

    The gradient of this line, I'll call it 'M', is \frac{-1}{3}

    The gradient of the perpendicular line will be \frac{-1}{M} - this is a general rule. Be careful with signs!

    So what will the gradient of the perpendicular be?

    Once you have it, you have a point and the gradient so forming an equation should be quite straightforward.
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