Help I can't integrate

[K.I.L.E.R]

http://www.mathwords.com/u/u_substitution.htm

Can someone explain this to me?
The idiots are pulling numbers out of their backsides.

 

[StefanS]

http://www.mathwords.com/u/u_substitution.htm

Can someone explain this to me?
The idiots are pulling numbers out of their backsides.

Unless you can be more specific about what you don't understand, I have a pretty hard time trying to figure out your problem.

 

[_xxx_]

Once you graduated, all your certificates belong to us! Well, for maths at least...

 

[K.I.L.E.R]

Unless you can be more specific about what you don't understand, I have a pretty hard time trying to figure out your problem.

y = 5 + x^2

du/dx = 0 + 2x

Now where does 1/2 du come from?

 

[StefanS]

y = 5 + x^2

du/dx = 0 + 2x

Now where does 1/2 du come from?

You're substitution functions: your u is a u(x), thus

u(x)=5+x^2 -> du(x)/dx=2x -> du=2x dx -> 1/2 du=x dx

which is then substituted in the original integral

EDIT: minor clarification

 

[dantruon]

y = 5 + x^2

du/dx = 0 + 2x

Now where does 1/2 du come from?

they divide it so that :

du=2xdx == 1/2du=xdx which is easier to substitute back into the original equation.

 

[K.I.L.E.R]

Ahh thanks.
I don't have to do that though?

they divide it so that :

du=2xdx == 1/2du=xdx which is easier to substitute back into the original equation.

 

[CosmoKramer]

I don't have to do that though?

You'll have to substitute dx, so however you do it (assuming you do the same u(x) substitution) it will amount to the same thing.