Question 82966
<font size = 4><b><pre>
Can someone please, please show me how to do this?
Write the equation of the line which has y-intercept (0, 5) and is
perpendicular to the line with equation y = –3x + 1.
I got y = –3x + 5. AM i right, am I close to being right?

----------------------------------

Your answer would have been correct if the word "perpendicular"
had been "parallel".

So you have confused "perpendicular" with "parallel"

Things to remember:

1.  Parallel lines have EQUAL slopes.
2.  Perpendicular lines have slopes which are formed by
    taking the reciprocal and changing the sign.

The slope of y = -3x + 1 is -3

Therefore a line which is perpendicular to it will have
the slope which is formed thusly:

Take -3.
Write it as {{{-3/1}}}
Invert it as {{{-1/3}}}
Change the sign and get {{{1/3}}}

So the slope of a line PERPENDICULAR to the line whose
equation is y = -3x + 1 is {{{1/3}}}

Now use the form:

     y = mx + b   where m = {{{1/3}}} and b = 5 

     y = {{{1/3}}}x + 5

That is the PERPENDICULAR line's equation.

Edwin</pre>