Linear algebra,

So I have to solve this:
http://screencast.com/t/LIVGVxu4i

And that's the solution:
http://screencast.com/t/yFaUG6lY

Can you please tell me why do I have to multiply the first equation by the number "2" ?

Thanks

Question

Linear algebra,

So I have to solve this:
http://screencast.com/t/LIVGVxu4i

And that's the solution:
http://screencast.com/t/yFaUG6lY

Can you please tell me why do I have to multiply the first equation by the number "2" ?

Thanks

christos · Answer

anonymous · Answer

You have to multiply by 2 because you need to have y by itself.

christos · Answer

so I multiply whatever canceles the y during addition ?

christos · Answer

addition of the 2 equations

anonymous · Answer

Technically, you need to get y by itself, that's what I've been told.

christos · Answer

ok thanks

anonymous · Answer

Wait you said you're adding the equations?

christos · Answer

Yeah the solution is demonstrated above

anonymous · Answer

Oh, well you have to multiply 2y by 2 to make it 4y. You want to make it 4y because the other equation has -4y. Therefore 4y + -4y = 0

anonymous · Answer

Are you following?

christos · Answer

yea yea I got it

anonymous · Answer

Okay, Good :)