integration,,either forgotton basics or wrong answer given

• Mar 29th 2011, 04:36 AM
fudge2011
integration,,either forgotton basics or wrong answer given
$$\int_{0}^{t}\frac{\alpha \beta \gamma^\alpha}{(\gamma+\beta t)^\alpha+1}[\math] comon seriously theres nothing wrong with my latex code.... be back in an hour with the 'wrong' anser they give. got to nip out i cant • Mar 29th 2011, 05:15 AM tonio Quote: Originally Posted by fudge2011 $\int_{0}^{t}\frac{\alpha \beta \gamma^\alpha}{(\gamma+\beta t)^\alpha+1}$ comon seriously theres nothing wrong with my latex code.... Yes there is: you must close with a backslash, not a front one: like this$$

I already did it for you.

Anyway, as you can see, what comes out is incomprehensible (at least for me)...is the variable "t"?

So you're trying to integrate with "dt"? Unlikely since the upper limit is "t", but

then I've no idea what you meant by that integral...(Punch)(Angry).

Tonio

be back in an hour with the 'wrong' anser they give. got to nip out

i cant

.
• Mar 29th 2011, 06:20 AM
fudge2011
Quote:

Originally Posted by tonio
.

ah thats it thanks.

yeahits with respect to d $\int_{0}^{t}\frac{\alpha \beta \gamma^\alpha}{(\gamma+\beta t)^{\alpha+1}}dt$ its to the power alpha+1 on the bottom not +1 separately nb(Bow)

and the answer given is $-\[\frac{\gamma^\alpha}{(\gamma+\beta t)^\alpha}]_{0}^{t}$

im not into the whole change the t to something like s then do ds , i just keep itas dt....but for this particular integral i keep getting $(\alpha+1)$ on the bottom which I cant caancel...something is wrong i just cant figure out if its me or not

my official working goes something like this,,,as i have forgotton the consise way of dealing with the t in the denominator or ,,woould have there been a differential of it on top the use of natural logs..here goes..
$=\int_{0}^{t}\alpha\beta\gamma^\alpha(\gamma+\beta t)^{-(\alpha+1)}dt\\
=\[-\frac{\alpha\beta\gamma^\alpha}{\beta(\alpha+1)(\g amma+\beta t)^\alpha}]_{0}^{t}$
this makes sense right?...obviously this procedes to a wroong answer'! (Worried)
• Mar 29th 2011, 07:06 AM
fudge2011
ah,,im supposwd to increase the power,,,how do i delete thread?
• Mar 29th 2011, 07:12 AM
HallsofIvy
I don't see any working, just the problem and what you claim to be the correct answer. Presumably you used the power rule for integrating but you appear to have used it incorrectly. The integral of $x^n$ is $\frac{1}{n+1}x^{n+1}$, not $\frac{1}{n}x^{n+ 1}$ as you have used. With $n= -(\alpha+ 1)= -\alpha- 1$, $n+ 1= -\alpha$. The integral of $(\gamma+ \beta t)^{-(\alpha+ 1)}$ is
$-\frac{1}{\alpha\beta}(\gamma+ \beta t)^{-\alpha}$

That will cancel both the $\alpha$ and $\beta$ in the numerator leaving
$-\frac{\gamma^\alpha}{(\gamma+ \beta t)^\alpha}\left]_0^t= 1- \frac{\gamma^\alpha}{(\gamma+ \beta t)^\alpha}$.