SOLUTION: Determine wether the line PQ is parallel or perpendicular or neither to a line with a slope of -2. P(-2,1) Q(6,5) I did the following:y-1=-2(x--2) y-1=-2x-4 y=-2x-3 i got this

Algebra ->  Proportions  -> Lessons -> SOLUTION: Determine wether the line PQ is parallel or perpendicular or neither to a line with a slope of -2. P(-2,1) Q(6,5) I did the following:y-1=-2(x--2) y-1=-2x-4 y=-2x-3 i got this      Log On


   

Question 162855This question is from textbook beginning and intermidiate algebra
: Determine wether the line PQ is parallel or perpendicular or neither to a line with a slope of -2. P(-2,1) Q(6,5)
I did the following:y-1=-2(x--2)
y-1=-2x-4
y=-2x-3 i got this for p
for Q
y-5=-2(x-6)
y-5=-2x+12
y=-2x+17 so i thought they were parallel; but they are perpendicular i got this one wrong on my test but i do not know what i did wrong please help This question is from textbook beginning and intermidiate algebra

Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
Note: you don't need to find the equation of the line, you only need the slopes of two lines to figure if they are parallel, perpendicular, or neither

Slope of PQ:


m=%28y%5B2%5D-y%5B1%5D%29%2F%28x%5B2%5D-x%5B1%5D%29 Start with the slope formula.


m=%285-1%29%2F%286--2%29 Plug in y%5B2%5D=5, y%5B1%5D=1, x%5B2%5D=6, and x%5B1%5D=-2. These values come from the points P(-2,1) and Q(6,5)


m=%284%29%2F%286--2%29 Subtract 1 from 5 to get 4


m=%284%29%2F%288%29 Subtract -2 from 6 to get 8


m=1%2F2 Reduce


So the slope of the line that goes through the points P(-2,1) and Q(6,5) is m=1%2F2


Since the product of the given slope -2 and the slope 1%2F2 is %28-2%29%281%2F2%29=-2%2F2=-1, this means that the two lines are perpendicular.


Note: you used the same slope twice to get your answer. You forgot to calculate the slope of the line that goes through PQ (see above)