[B]Integration ~ Substitution Method HELP???[/B] (1 Viewer)

[MysteryMoon]

I'm just confused as to how it works.
I've been trying to solve this equation: x (2x + 7) , let u = 2x + 7

So this is what I did:

du/dx = 2

du/2 = dx <-- this is where I'm stuck (cuz apparently the right side is meant to be the derivative of 2x + 7 but there's an x in x(2x + 7) so I'm so confused now........

Seriously, I don't even understand myself. =_=

I just don't get the concept of it. Any help would be appreciated.

 

[Squar3root]

Just expand and integrate lol

 

[integral95]

I'm just confused as to how it works.
I've been trying to solve this equation: x (2x + 7) , let u = 2x + 7

So this is what I did:

du/dx = 2

du/2 = dx <-- this is where I'm stuck (cuz apparently the right side is meant to be the derivative of 2x + 7 but there's an x in x(2x + 7) so I'm so confused now........

Seriously, I don't even understand myself. =_=

I just don't get the concept of it. Any help would be appreciated.

I'm assuming you mean



your step is correct so far,regarding the bolded part it doesn't have to be.

 

[integral95]

Just expand and integrate lol

yeah i'd probably just do that haha

 

[MysteryMoon]

How do I expand it tho?

 

[Squar3root]

How do I expand it tho?

Not sure if srs

 

[MysteryMoon]

@ Integral95

Okay, I kinda get it! Thnx

 

[MysteryMoon]

Not sure if srs

I am serious. =_= Like how would you expand x(2x + 7)^1/2 then? It's expanding with a fractional indice......... (or am I muddling myself up???)

 

[Squar3root]

I am serious. =_= Like how would you expand x(2x + 7)^1/2 then? It's expanding with a fractional indice......... (or am I muddling myself up???)

Oops didn't see the 1/2

It would be better to let u^2 = 2x+7

 

[anomalousdecay]

Oops didn't see the 1/2

It would be better to let u^2 = 2x+7

Even better, let u = (2x + 7)^(1/2) so that you don't have to worry about negative case when taking the squar3root with what you did above.

 

[Squar3root]

Even better, let u = (2x + 7)^(1/2) so that you don't have to worry about negative case when taking the squar3root with what you did above.

Nah my way is better