How do you find the slope that is perpendicular to the line #3x-9y=15#?

1 Answer
Jul 29, 2016

Answer:

The slope of the line perpendicular to line #3x-9y=15# is #-3#

Explanation:

When using the equation of a line, one calculates the value of #y# in terms of #x#, say #y=mx+c#, then #m# is the slope of the line and #c# is its intercept on #y#-axis.

As #3x-9y=15# can be written as #3x-15=9y# or

#y=3/9x-15/9# or #y=1/3x-5/3#

Hence slope of #3x-9y=15# is #1/3#

Product of slopes of two perpendicular lines is #-1#

Hence, the slope of the line that is perpendicular to the line #3x-9y=15# is #-1/(1/3)=-1xx3/1=-3#

graph{(3x-9y-15)(3x+y+5)=0 [-10, 10, -7.04, 2.96]}