A Difficult Equation

[Poweranimals]

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

[Math Is Hard]

Hint: If two lines are perpendicular, what does this tell you about their slopes?

[Poweranimals]

They intersect?

[Math Is Hard]

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.

[NSX]

opposite reciprocal?

:P

I prefer to use the term negative reciprocal.

[Math Is Hard]

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!

[Math Is Hard]

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.

[Math Is Hard]

so if the slope of a line is -1/4, then the slope of a line that is perpendicular to it would be...?

[gazzo]

or when you multiply both slopes together you get -1 ?

my maths teacher had a strange way of explaining things...

[abertram28]

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.