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Mathematics 17 Online
OpenStudy (anonymous):

Attached.

OpenStudy (anonymous):

OpenStudy (phi):

do you know how to write the equation of a line using vectors?

OpenStudy (anonymous):

Yeah. I got one point already.

OpenStudy (anonymous):

I got (4.4, 5.2)

OpenStudy (phi):

a "direction vector" from E to F is (F-E) normalize this to unit length v= (F-E)/|F-E| now start at E and go in the direction v 3 units E+3v or E-3v

OpenStudy (phi):

ya follo' ?

OpenStudy (anonymous):

I think so.

OpenStudy (anonymous):

So I'm not sure where to go from here though. I have vector (8, -6) and I scaled it by 3/10 to get my last point. But how do I get the second one?

OpenStudy (phi):

F-E = (10,1) - (2,7)= (8,-6) that is the direction from E to F its magnitude is sqrt(64+36)= sqrt(100)= 10 so the unit length vector is (8/10, -6/10) or (0.8, -0.6) call this v= (0.8,-0.6) if we start at E and add v to it, we move 1 unit toward F if we add 3v, we move 3 units away from E (toward F) this means E+3v= (2,7) + 3(0.8, -0.6) = (2,7) + (2.4, -1.8) = (4.4, 5.2)

OpenStudy (phi):

now go in the opposite direction, go to point E -3v

OpenStudy (phi):

here is a picture |dw:1354731320487:dw|

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