Coordinate Geometry Help (1 Viewer)

bujolover

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Hi guys,
Could you please tell me if I got the answer to this question right?
The lines 8x + qy + 6 = 0 and 3x − 4y + 4 = 0 are perpendicular. Find the value of q.
I got q = -6, but the answer says 6. I'm guessing a typo?
 

boredofstudiesuser1

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Yes, the answer is supposed to be 6.

By putting them into y = mx + b

y1 = (-8/q)x + (6/q)

y2 = (3/4)x + (4/4)

We can see gradient y1 = -8/q

And gradient y2 = 3/4

my1 * my2 = -1

So -8/q = negative reciprocal of 3/4

-8/q = -4/3

8/q = 4/3 (divide both sides by negative)

24 = 4q

q = 6

Not sure how this is Extension 1 though...
 
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1729

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Hi guys,
Could you please tell me if I got the answer to this question right?
The lines 8x + qy + 6 = 0 and 3x − 4y + 4 = 0 are perpendicular. Find the value of q.
I got q = -6, but the answer says 6. I'm guessing a typo?
 

bujolover

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Yes, the answer is supposed to be 6.

By putting them into y = mx + b

y1 = (-8/q)x + (6/q)

y2 = (3/4)x + (4/4)

We can see gradient y1 = -8/q

And gradient y2 = 3/4

my1 * my2 = -1

So -8/q = negative reciprocal of 3/4

-8/q = -4/3

8/q = 4/3 (divide both sides by negative)

24 = 4q

q = 6
Ah, ok thanks. :)

Not sure how this is Extension 1 though...
IDK. This was a part of a worksheet that I found as part of Extension 1 work, I believe...
 

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