I give up...

[ManBearPig]

Anyone wanna try? Compute the indefinite integral:

?[ 4 x/(v{x^2 + 2})]

i got: dx = 4((x^2+2)^-(3/2)) / 3

it's wrong though. anyone?!!?

thanks

 

[Brainonska511]

Just use u substitution:

u = x^2 + 2
du = 2x dx

so you get Integral of (2u^(-1/2))du

So you should get 4u^(1/2) which gives you 4sqrt(x^2 + 2) + c

 

[blurredvision]

I look at that, and thank the lord that I will never have to use that kind of math as long as I live.

 

[evetstech]

4v(x^2 +2)

 

[xSauronx]

Originally posted by: blurredvision
I look at that, and thank the lord that I will never have to use that kind of math as long as I live.

qft. i could barely do high school algebra if i had to (my high school education sucked it, and i havent done algebra in almost 8 years)

 

[TecHNooB]

Nm

 

[hypn0tik]

Originally posted by: TecHNooB
Looks like an inverse trig.. lemme try and solve this

Nope. Simple substitution.

If the factor of x wasn't out in front, it would be a trig substitution where you'd substitute:

cos(t) = sqrt(2)/sqrt(x^2+2). --> 1/sqrt(x^2+2) = cos(t)/sqrt(2) and go from there.

 

[ManBearPig]

man these are all so hard for me...you guys are using methods we havent learned to solve them

thanks for the help!

 

[ManBearPig]

Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

 

[Captante]

As far as I'm concerned those might as well be hieroglyphics!

 

[ManyBeers]

Originally posted by: Kazaam
Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

Here let me take a stab at it..............................................nope, sorry pal.

 

[MovingTarget]

u substitution is probably the best method as described above. Just don't forget the "+C" constant of integration at the end.

I am a math grad student. I got a C in high school algebra.

Calculus may look scary, but believe me, there is a lot more to math that you might be good at. Problem is, you don't get to the fun stuff until its too late for most people. Good luck!

 

[ManBearPig]

Thanks guys...yeah u substitution is what the homework is over. I'm having problems though, lol.

 

[TecHNooB]

Originally posted by: MovingTarget
u substitution is probably the best method as described above. Just don't forget the "+C" constant of integration at the end.

I am a math grad student. I got a C in high school algebra.

Calculus may look scary, but believe me, there is a lot more to math that you might be good at. Problem is, you don't get to the fun stuff until its too late for most people. Good luck!

Fun stuff? Theoretical math is all gibberish I tell ya!

 

[QurazyQuisp]

Originally posted by: Kazaam
Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

errr... (forget the by parts)

U = 36x^2
du = 72xdx

?3(e^u)/72du
3(e^u)/72 + c => e^(36x)^2/24 +c

 

[hypn0tik]

Originally posted by: Kazaam
Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

Here, you have 3x being multiplied by your exponential which is a function of x^2. Just like the previous problem, you want to use a substitution.

The form of your integral is correct, but you need to be careful with your constants.

 

[ManBearPig]

Originally posted by: QurazyQuisp

Originally posted by: Kazaam
Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

errr... (forget the by parts)

U = 36x^2
du = 72xdx

?3(e^u)/72du
3(e^u)/72 + c => e^(36x)^2/24 +c

err thats not right. how'd you get 36x? itd be -12x

im still getting (1/-4)e^(-6x)^2 which seems right, i dunno. but its not right lol. ahh

 

[magomago]

Originally posted by: blurredvision
I look at that, and thank the lord that I will never have to use that kind of math as long as I live.

And I look at that and go "Damn...it feels good to know that I think its straight forward to solve that kind of math!"

 

[hypn0tik]

Originally posted by: Kazaam

Originally posted by: QurazyQuisp

Originally posted by: Kazaam
Ok, honestly I am not looking for the answer, but why is this not right? If someone could point me in the right direction that'd be great.

solve ? 3xe^(-6x)^2

i got: e^(-6x)^2 / -4

which is wrong. ahhhhhh

errr... (forget the by parts)

U = 36x^2
du = 72xdx

?3(e^u)/72du
3(e^u)/72 + c => e^(36x)^2/24 +c

err thats not right. how'd you get 36x? itd be -12x

im still getting (1/-4)e^(-6x)^2 which seems right, i dunno. but its not right lol. ahh

Re-write the problem like this:

?3xe^(-6x)^2 dx = 3?x e^(36x^2) dx

Let u = x^2 -> du = 2xdx --> xdx = 1/2 du

Your integral becomes:

3/2 ? e^36u du

Which you should be able to solve from there.

 

[XZeroII]

This will teach you everything you need to know about math...