Coordinate Geometry Help (1 Viewer)

[bujolover]

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]

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

m_y1 * m_y2 = -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...

 

[1729]

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]

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

m_y1 * m_y2 = -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...