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Solve 2x + y + y' x = 3y^2 y', why is this wrong?

  • Thread starter Ry122
  • Start date
  • #1
565
2
2x+y+(dy/dx)x=3y^2(dy/dx)
This is wrong:
(dy/dx)(x-3y^2)=-2x-y
This is right:
2x+y=(3y^2-x)(dy/dx)

Can someone please explain why.
 

Answers and Replies

  • #2
This is wrong:
(dy/dx)(x-3y^2)=-2x-y
This is right:
2x+y=(3y^2-x)(dy/dx)

Those two equalities are actually the same, so I'm not sure "right" and "wrong" really apply.
The only difference is that the second is the negative of the first.
If you move each side of the first equality over the equals sign you will get the second
 
  • #3
Defennder
Homework Helper
2,591
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Yeah, scottie_000 is right. Multiply the first by -1 and you'll get the second.
 
  • #4
565
2
So either answer would be correct in an exam?
 
  • #5
Defennder
Homework Helper
2,591
5
Of course, if they were strictly equivalent and your teachers don't mind.
 

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