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## otakugirl 2 years ago Select the equations that are parallel and perpendicular to y =1/4x + 7 and that pass through the point (-8, 9). a) parallel: y =1/4x - 11 perpendicular: y = -4x + 23 b) parallel: y = -4x + 11 perpendicular: y =1/4 x - 4 c)parallel: y = 4x - 7 perpendicular: y =1/4x - 7 d)parallel: y =1/4x + 11 perpendicular: y = -4x - 23

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1. otakugirl

help?

2. aroub

Oh my x_x This what I'm going to do, I'll explain to you the first one and you do the rest and I'll check them, deal? :)

3. otakugirl

okay deal :)

4. aroub

Do you know what does parallel and perpendicular mean here?

5. otakugirl

a little bit not so much :/

6. aroub

It's okay, what do you know?

7. otakugirl

okay i know that perpendicular lines intersect at a 90 degree angle and parallel lines dont intersect

8. aroub

Okay, the meaning in here for both is all about the slope. Parallel means that they have the same slope while in perpendicular the slope is the opposite reciprocal of the original slope.

9. otakugirl

ohh okay i got it.

10. aroub

For a) parallel: y =1/4x - 11 ; (-8,9) slope= 1/4 ; x=-8 , y=9 ( I got x and y from (-8,9) ) To solve such problem you will have to use the slope intercept form, which is: y=mx+b, where m is the slope. Now all you got to do is substitute to find b. => 9=1/4(-8)+b 9=-2+b 11=b since we found" b" we can now find the new equation which is parallel to the original equation. How? By using the slope intercept form, again! y=mx+b, you always leave the x and y! Just substitute for m and b. => y=1/4x+11 Got it?

11. otakugirl

yes thank you so much :)

12. aroub

Can you do the perpendicular now? They're the exact same steps but with different slopes of course. Remember the slope of the perpendicular is the opposite reciprocal.

13. aroub

I say -4, agree?

14. otakugirl

yes now i can do it and i agree with -4

15. aroub

Great ^_^

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