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A Difficult Equation

  1. Jul 10, 2004 #1
    Perpendicular to y = -1/4x - 12 passing through (3, -4).
     
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  3. Jul 11, 2004 #2

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    Hint: If two lines are perpendicular, what does this tell you about their slopes?
     
  4. Jul 11, 2004 #3
    They intersect?
     
  5. Jul 11, 2004 #4

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    well, the lines intersect, yes. but you know what the slope of the first line is, right? your equation is in y =mx+b format so you can tell just by looking.

    the slope of the second line will be the opposite reciprocal of the first slope.
     
  6. Jul 11, 2004 #5

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    opposite reciprocal?

    :P

    I prefer to use the term negative reciprocal.
     
  7. Jul 11, 2004 #6

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    I grew fond of "opposite" because there's no confusion if you are talking about the slope of a line that's perp to a line with a negative slope. but that's just me!
     
  8. Jul 11, 2004 #7

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    anyhoo, power animals, what we're saying is that if a line has a slope of positive 3, for example, then the slope of a line that is perpendicular to it would be -1/3.
     
  9. Jul 11, 2004 #8

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    so if the slope of a line is -1/4, then the slope of a line that is perpendicular to it would be...?
     
  10. Jul 11, 2004 #9
    or when you multiply both slopes together you get -1 ?

    my maths teacher had a strange way of explaining things...
     
  11. Jul 12, 2004 #10
    yes. when multiplied together they will equal -1

    so you can see it by setting -1=m1*m2 where m1 or m2 to -1/4.

    do you need help finding the whole equation based on that slope and point? you can just plug an x and a y into the y=mx+b way and solve for b too.
     
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