Any1 here know maths?

[Phobos]

Probably stupid to ask here, but anyway..

y'= 1+y/x
substitute: u= y/x => y= u.x

now I get:
y'= u'.x+u

but why? how did I get that :/

 

[ObitoRolent]

Answer: Through math.

 

[RedRobin]

Eh post a pic of the problem, I cant see it like that.

 

[DotHack3r]

Dude who or what demon gave you that question

 

[Dantе]

should be y=1+u

 

[End of Days]

but its correct

 

[NARUTO BONED SASUKE]

post pic?.........

 

[Tenasa Uchiha]

Naw man sorry

 

[Phobos]

Eh post a pic of the problem, I cant see it like that.

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but its correct

Yeah, but how did i get that?

 

[Lt Fresh]

Are you doing derivatives through U substitution and partial derivatives?

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Yeah, but how did i get that?

Does u.x mean u times x? That's what I'm assuming.
-It looks like you're doing U substitution for y/x and then doing an integral(reverse derivative) of y' to find y=u*x

 

[Phobos]

Are you doing derivatives through U substitution and partial derivatives?


Does u.x mean u times x? That's what I'm assuming.
-It looks like you're doing U substitution for y/x and then doing an integral(reverse derivative) of y' to find y=u*x

U is subsititution for y/x, so u=y/x from that you can easily see that y=u*x

but what I don't get is how did I get the last part, how did I get that y'=u'*x+u

 

[I Don]

In which variable's respect are you differentiating the said equation?

 

[RedRobin]

Were you trying to find y''?

 

[Phobos]

In which variable's respect are you differentiating the said equation?

The question is "solve: y' = 1 + y/x"
the answer is y = x ln |x| + C x

but I don't get that one step, no idea how to get y'=u'*x+u

 

[Lt Fresh]

U is subsititution for y/x, so u=y/x from that you can easily see that y=u*x

but what I don't get is how did I get the last part, how did I get that y'=u'*x+u

Alright if U=y/x that means U'=1/x (I did the derivative of U with respect to x) then this puts y' as y'=u'*x+u put back in what you subbed out you'll have y'=(1/x)*x+(y/x). Then (1/x)*x equals 1 so in the end your back to y'=1+(y/x)

-So to sum in up you subbed y/x to equal U
-Then you did the derivative of U to get 1/x equals U'
-put both U and U' back into the equation and you're set

 

[Phobos]

Alright if U=y/x that means U'=1/x (I did the derivative of U with respect to x) then this puts y' as y'=u'*x+u put back in what you subbed out you'll have y'=(1/x)*x+(y/x). Then (1/x)*x equals 1 so in the end your back to y'=1+(y/x)

-So to sum in up you subbed y/x to equal U
-Then you did the derivative of U to get 1/x equals U'
-put both U and U' back into the equation and you're set

I still don't get it if you derivate y/x won't the outcome be -y*x^(-2)? how come it's 1/x?

oh shit, I shoud derivate the "y" not the "x" right? I'm so retarded.

 

[Lt Fresh]

I still don't get it if you derivate y/x won't the outcome be -y*x^(-2)? how come it's 1/x?

-It depends on what you're holding constant or in other words what variable are you differentiating.
So if you do dx/dy of y/x then your answer would be 1/x
but if you do dy/dx of y/x then you get what you thought would be the out come (-y*x^(-2))

I'm assuming you're differentiating in respect to x in the equation I believe

 

[Lt Fresh]

The question is "solve: y' = 1 + y/x"
the answer is y = x ln |x| + C x

but I don't get that one step, no idea how to get y'=u'*x+u

Do you need help with this too?

 

[Phobos]

Do you need help with this too?

Nah, the rest is fine, thanks.

Just that one step confused me to all hell.

 

[Zee Seh]

Well seems like the question is answered. :| I wanted to answer it doe >,>