The slope of a line that is perpendicular to the line y - 3x = 12, is:

Question

mattfeury · Answer

what is the slope of this line?

saifoo.khan · Answer

perpendicular line as the slope, the inverse of the original line!

anonymous · Answer

so..-1/3?

mattfeury · Answer

i don't think -3 is quite the slope ;)

saifoo.khan · Answer

NO, look.
the original slope is:
-3.

so not insert this value in the formulae:

$$\large m_1 * m_2 = -1$$

$$-3 * m_2 = -1 $$
$$m_2 = \frac{-1}{-3} $$
$$m_2 = \frac{1}{3}$$

anonymous · Answer

oooh

mattfeury · Answer

the original slope is 3. you need to put it in slope-intercept form:

y = mx + b

saifoo.khan · Answer

LOl, my bad.. 
chnge tht -3 into +3!!

sorry!

so the final answer will be:

$$m= \frac{-1}{3}$$

anonymous · Answer

you can think of that with angles..

m = 3 => tan(x) = 3 (=) x = 71.56º

now you just need to add or subtract 90º

it's like 71.56+-90 = +-18.43

tan(+-18.43) = +-1/3


personally I think the graphical way is more simple to understand