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Question 728542: Write the equation of the line that is perpendicular to the following line that goes through the given point.
y=2x+3; (2,-1)
Answer by ohtheirony(35)   (Show Source):
You can put this solution on YOUR website! A line parallel to another line has the same slope. A line perpendicular to a line has the opposite sign reciprocal of the slope.
So what is an opposite sign reciprocal, or reciprocal in general? A reciprocal is basically an upside down fraction. For example, the reciprocal of 3/5 is 5/3, or the reciprocal of 5 is 1/5. To make a reciprocal an opposite sign reciprocal, just change it to the opposite positive or negative. The opposite sign reciprocal of 3/5 would be -5/3.
I'm pretty sure you mean (2,-1) should be (-2,-1), otherwise the equation 2x+3=y would be wrong. Point (0,3) can be found by putting 0 in as x and solving the equation 2x+3=y. We can now find our slope using the two points.
The slope of the equation is 2. (If you don't know how to find slope, see the link below) The opposite sign reciprocal of 2 is -1/2, so the slope for your perpendicular line is -1/2.
How to find slope: http://www.mathwarehouse.com/algebra/linear_equation/slope-of-a-line.php
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