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Help? :(

wat

I need some help with this problem

ok

wats ur answer

I dont have onne, I need help :| I attached a link of the problem

i did

hold on

thnx (:

Do you still need help?

Yes please (:

ya

Okay, Do you know how to even start working on this problem?

No :C

So are you working with vectors?

indeed I am!

Im just tottally lost on this problem

Ok, so have you done vector proofs before?

no neverO=

ok, so ob+ba=oa

0=(0,0) A=(x1,y1) B=(x2,y2)

Vector BA=A-B=(x1-x2, y1-y2)

okk

Good so far?

All what you have to do now is find vecotor OA and vecotr OB

O: oh really but is there like another pic you have to draw/

no

oh cool

|dw:1352869007184:dw|

so vector BA is equal to A-B
so when you subtract the points element-wise
you get x1-x2 and y1-y2

|dw:1352869116355:dw|

Oh right, now I find Oa Ob ?How can I do thta again?

|dw:1352869175679:dw|

now you do the same for vector ob

|dw:1352869297947:dw|

So OB is OB = O-B= <0-x2 , 0-y2 > ?

no, it would be = B-O =

So, now you need to subtract from . to prove that it equals

ohhh right!

look at the attachment, the circled ones.

How would you prove the?

*them?

They are equal.

so, by the subtraction of the vectors, you prove that = -

OH theyre equal!!
Its < x1-x2 , y1-y2 > !

pretty much.

Now to solve part 2, set point c equal to (x3, y3)

So all what xOA is saying is to ditribute the x?

Ya

Oh okay yy

|dw:1352870110521:dw|

right?

yes.

Cool thanks ((:

you want me to isolare c from (C-B)/(A-C) =x/y
right?

yes,

u see, how i got, (C-B)/(A-C) =x/y
from given condition, / =x/y

Wait how would you do that because C is being subtracted

u mean how to isolate C ?
cross-multiply....

yea youd get y(c-b) = x(a-c) ...

try to isolate C from that...

so I distribute..first then

yc-cb = xa - xc

yes, distribute then bring all terms with 'c' together, then factor out c

its yc-yb on the left...

So C= xa-xc / (y-b)

there, u were not able to isolate C, notice, c is there on right side also

yc-yb = xa - xc
yc+xc = xa+yb
got this step ?

now can u isolate c ?

I thought ititd be yc-cb = xa - xc since u cross mult tho..

|dw:1352871594989:dw|

|dw:1352871643318:dw|

right x)

|dw:1352871704757:dw|

yesyes i did that xD

what does left side simplify to ?

knowing that its given that x+y=1

C= xa+yb / y+x

what is x+y= ?

Wait but does C equal to that O:

yes.

oh okay lol Um y+x = .. ?

its given to be =1
see the question

Oh cool so it would just be xa+yb

yes, c=xa+yb
now u know what to do next ?

PLug it to...

we know that C=(x3,y3)
and O=(0,0)
so can you find = ?

which is ?

x3,y3

so =C
so we can replace C by
right ?

ohhyeauhhh! ool!

in same way, we can replace A by ... ?
B by ... ?

A with x1,y1??

A with

yes..

so put all those in
c=xa+y
and see whether u get what needs to be proven..

|dw:1352872625517:dw|

Do u mean plug in the value sliket his

|dw:1352872688272:dw|

OH THATS what you ment I tots get that!

all steps clear ? any doubts ?

Wait and how did u kno that OC=c and OA =A and OB = B ?

C = (x3,y3)
=C-O = (x3,y3)-(0,0) = (x3-0,y3-0) = (x3,y3) = C
same for A and b

got it ?

same type ? ....actually even i need to go in few minutes...

lets me see the question atleast

OK but && Oh and alsoo how did you know that ( C- B)/(A-C) = x/y

it is given that BC /CA = x/y
now
BC=C-B
CA=A-C

remember for any vector XY, we can write it as Y-X

oh okay why is it flipped again?

flipped again ? means ?

Oh I mean like why isnt it like BC= B-c instead its C-B

so its no difference, just a way of representation

Oh right k thnx!
lemme post the other problem I dont think we have enough tim :C