A Difficult Equation

  • #1

Main Question or Discussion Point

Perpendicular to y = -1/4x - 12 passing through (3, -4).
 

Answers and Replies

  • #2
Math Is Hard
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Hint: If two lines are perpendicular, what does this tell you about their slopes?
 
  • #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.
 
  • #5
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opposite reciprocal?

:P

I prefer to use the term negative reciprocal.
 
  • #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!
 
  • #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.
 
  • #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...?
 
  • #9
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or when you multiply both slopes together you get -1 ?

my maths teacher had a strange way of explaining things...
 
  • #10
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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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