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Question 446858: Find the slope of AC and BD. Decide whether AC is perpendicular to BD.
A(-1,-2) B(-3,2) C(0,1) D(3,0)
Found 2 solutions by mananth, ikleyn:
Answer by mananth(16949)   (Show Source):
You can put this solution on YOUR website! Slope of Line Ac
x1 y1 x2 y2
-1 -2 0 1
slope m =(y2-y1)/(x2-x1)
(1-(-2)/(0-1)
(3/1)
m=3
Slope of line BD
x1 y1 x2 y2
-3 2 3 0
slope m =(y2-y1)/(x2-x1)
(0-2)/( 3-(-3) )
(-2/6)
m=-0.33
m1*m2=-1
so the lines are perpendicular
Answer by ikleyn(53595)  (Show Source):
You can put this solution on YOUR website! .
Find the slope of AC and BD. Decide whether AC is perpendicular to BD.
A(-1,-2) B(-3,2) C(0,1) D(3,0)
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The solution in the post by @mananth is presented in monstrous form.
He correctly determined that m1 = 1/3, but then he writes m2 = -0.33.
This is wrong. What is TRUE, is that m2 = -1/3, but not -0.33.
So, the correct presentation should be as showed below.
Slope of Line Ac
x1 y1 x2 y2
-1 -2 0 1
slope m1 =(y2-y1)/(x2-x1)
(1-(-2)/(0-1)
(3/1)
m1 = 3
Slope of line BD
x1 y1 x2 y2
-3 2 3 0
slope m2 =(y2-y1)/(x2-x1)
(0-2)/( 3-(-3) )
(-2/6)
m2 = -1/3
m1*m2=-1
so the lines are perpendicular
This is the correct form to present the solution.
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For @mananth, -1/3 and -0.33 is the same value, but it is not true - they are DIFFERENT !
In Math, to teach that -0.33 is the same as -1/3 - this is a CRIME ( ! )
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