Can someone help me with this problem

**10164064** · July 1st 2008, 09:04 PM

(e^x/10 - x^2 - 1)dx {5
{-5

**Mathstud28** · July 1st 2008, 09:07 PM

Originally Posted by 10164064

(e^x/10 - x^2 - 1)dx {5
{-5

With my super amazing mind-reading ablilities...this reads

$\int_{-5}^{5}e^{\frac{x}{10}}-x^2-1~~dx$

Well I will compute the antiderivative and you do the definite part

$\int{e^{\frac{x}{10}}~dx}=10\int{u}~du=10e^{\frac{ x}{10}}$

Now what substitution did I make?

$\int{x^2}~dx=\frac{x^3}{3}\longleftarrow\text{no surprises here}$

$\int~dx=x\longleftarrow\text{none here either}$

**10164064** · July 1st 2008, 09:10 PM

right i got that part but when I plug in the 5 and -5 I keep getting a negative answer when i subtract it

**Mathstud28** · July 1st 2008, 09:18 PM

Originally Posted by 10164064

right i got that part but when I plug in the 5 and -5 I keep getting a negative answer when i subtract it

The answer is negative.

**10164064** · July 1st 2008, 09:23 PM

Ok thank you I just thought I was doing something wrong

**Mathstud28** · July 1st 2008, 09:26 PM

Originally Posted by 10164064

Ok thank you I just thought I was doing something wrong

Well since

$\int_a^{b}f(x)~dx=F(b)-F(a)$ it is easily assumable that an integral can assume a negative value.

**CaptainBlack** · July 1st 2008, 10:51 PM

Originally Posted by 10164064

(e^x/10 - x^2 - 1)dx {5
{-5

Use brackets to make your meaning clear:

Something like:

integral [e^(x/10) - x^2 - 1] dx from -5 to 5

RonL

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