Eqn of lines parallel, perp. to y = 3x + 7 through (2, 3)

[machele]

I don't know where to start with this question:

Find the equation of a line parallel to a given line and a line perpendicular to the given line through a given point

y=3x+7, P(2,3)

I think I have to find the slope and then apply it to a new line, but she hasn't gone over this!

mathphobic

 

[jwpaine]

Use the point-slope form for the equation of a line: \(\displaystyle \L y - y_1 = m(x - x_1),\) where \(\displaystyle (x_1, y_1)\) are values from your ordered pair.

You already know your slope is m = 3.

The slope of a line parallel to another will have the same slope; the slope of a line perpendicular will have a slope such that slope m(p) = -1 where p is the slope perpendicular to m so if your slope m = 3, than the slope of the line perpendicular will be -(1/3)

With your new perpendicular slope, you can use the point-slope equation and plug in your values - solve in the form of y=mx+b

John

 

[Denis]

You can use google and get loads of sites to help you, like:
http://www.okc.cc.ok.us/maustin/Equatio ... 20Line.htm