Question 684323: How do I find the slope of a line perpendicular (8,12)(3.9)
Found 2 solutions by ReadingBoosters, MathLover1:
Answer by ReadingBoosters(3246)   (Show Source):
You can put this solution on YOUR website! First find slope using (8, 12) and (3, 9)
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A perpendicular line will have a negative inverse/reciprocal slope of 
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Answer by MathLover1(20850)  (Show Source):
You can put this solution on YOUR website! first find a line that passes through given point ( , )and has slope 
| Solved by pluggable solver: FIND a line by slope and one point |
What we know about the line whose equation we are trying to find out:
- it goes through point (8, 12)
- it has a slope of 3.9
First, let's draw a diagram of the coordinate system with point (8, 12) plotted with a little blue dot:
Write this down: the formula for the equation, given point  and intercept a, is
 (see a paragraph below explaining why this formula is correct)
Given that a=3.9, and  , we have the equation of the line:
Explanation: Why did we use formula  ? Explanation goes here. We are trying to find equation y=ax+b. The value of slope (a) is already given to us. We need to find b. If a point ( ,  ) lies on the line, it means that it satisfies the equation of the line. So, our equation holds for (, ):  Here, we know a, , and , and do not know b. It is easy to find out:  . So, then, the equation of the line is:  .
Here's the graph:
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now we can find the slope of a line perpendicular to a line  which passes through given points
perpendicular line has a slope 
| Solved by pluggable solver: FIND a line by slope and one point |
What we know about the line whose equation we are trying to find out:
- it goes through point (8, 12)
- it has a slope of -0.26
First, let's draw a diagram of the coordinate system with point (8, 12) plotted with a little blue dot:
Write this down: the formula for the equation, given point and intercept a, is
(see a paragraph below explaining why this formula is correct)
Given that a=-0.26, and , we have the equation of the line:
Explanation: Why did we use formula ? Explanation goes here. We are trying to find equation y=ax+b. The value of slope (a) is already given to us. We need to find b. If a point (, ) lies on the line, it means that it satisfies the equation of the line. So, our equation holds for (, ): Here, we know a, , and , and do not know b. It is easy to find out: . So, then, the equation of the line is: .
Here's the graph:
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