## anonymous one year ago Lines k and p are perpendicular, neither is vertical and p passes through the origin. Which is greater? A. The product of the slopes of lines k and p B. The product of the y-intercepts of lines k and p

1. anonymous

Perpendicular lines have opposite reciprocal slope. If we say the slope of line k is $$m$$, then the slope of line p would have to be $$(-\frac{ 1 }{ m})$$. What's $m * \frac{ -1 }{ m }$

2. anonymous

-1

3. anonymous

right, so we know the result for A is -1.

4. anonymous

wait why is it -1? how did u get that?

5. anonymous

That's what we just did. I was just restating the result

6. anonymous

I don't understand how we got that....

7. anonymous

we got -1 from the multiplication you did. m*(-1/m)

8. anonymous

yea but where and how did u get that?

9. anonymous

Perpendicular lines have opposite reciprocal slope. If we say the slope of line k is m, then the slope of line p would have to be (−1/m).

10. anonymous

oh okay. but for the problem itself it didn't give the slope

11. anonymous

we don't need to know the slope. Knowing the relationship between the two lines is enough because they don't ask for the actual slopes. They only ask for their products

12. anonymous

hmmmm ok

13. anonymous

so whats next?

14. anonymous

now we look at B. It says line p passes through the origin, so that means its y-intercept is 0. We don't need to know the y-intercept of line k because any number multiplied by 0, is 0. That means the result for B is 0.

15. anonymous

Okay so i get B but for A how do we know it's a positive slope and not a negative one?

16. anonymous

|dw:1439429848426:dw|

17. anonymous

it doesn't matter. If we said k had a slope of -m, then the opposite reciprocal of that would be 1/m. When you multiply you'd still get -1

18. anonymous

|dw:1439429888384:dw|

19. anonymous

OHHHHHHHHHHHHHHHHHHHHHHHHHHHH because they're perpendicular they will automatically be a negative for the product!!!!!!!!!!!!!!

20. anonymous

<333333 thank you

21. anonymous

right :)

22. anonymous

you're welcome

23. anonymous

so B is greater

24. anonymous

yes

25. anonymous

thank u =)