# equation of a line perpendicular to the line defined

• Jun 6th 2007, 05:19 AM
Alexander
equation of a line perpendicular to the line defined
which one of the following is the equation of a line perpendicular to the line defined by 3x -5y = 2?

1. 3x + 5y = 2
2. -3x + 5y = 2
3. 5x - 3y = 2
4. 5x + 3y = 2
5. there is not enough information to answer the question.
• Jun 6th 2007, 08:58 AM
Jhevon
Quote:

Originally Posted by Alexander
which one of the following is the equation of a line perpendicular to the line defined by 3x -5y = 2?

1. 3x + 5y = 2
2. -3x + 5y = 2
3. 5x - 3y = 2
4. 5x + 3y = 2
5. there is not enough information to answer the question.

Two lines are said to be perpendicular if their slopes are nagative inverses of each other. That is, if the slope of one line is m, then the slope of the other will be - 1/m .

You can go through the trouble of writting the lines in the slope-intercept form, that is, y = mx + b where you can see the slopes explicitly. Or you can just look at the equations and figure out what the slopes would be if you did rewrite them--it's not that hard. When you have identitfied the slopes, then make your choice. The answer is not choice 5, i will tell you that much
• Jun 6th 2007, 09:02 AM
Krizalid
$\displaystyle 3x-5y=2\iff{y=\frac15(3x-2)}$

The slope of the ortogonal line to this one is $\displaystyle -\frac53$, as Jhevon said.