Question

can somebody help me integrate (3+x)e^(-x)???i need as soon as possible

Answer 1

just multiply it out and work it in pieces

Answer 2

eiterh way youll have to play with integration by parts for a little bit

Answer 3

say, u = 3+x ; du = dx
u-3 = x

integrate u e^(u-3) du

Answer 4

i forgot that negative in your exponent

u e^(3-u) du

Answer 5

that still has a by parts in it, so either way you go your gonna have to get your hands dirty

Answer 6

so if my answer is [e^{-x} +xe^{-x} + c \] is wrong?

Answer 7

dunno, i would have to see how you worked it out

Answer 8

im sure theres a 3 in there someplace thats missing

Answer 9

i good dbl chk is to take the derivative of what youve got and see if it becomes the stuff you had to begin with

Answer 10

[e^{-x} +xe^{-x} + c ]' = -e^(-x) - x e^(-x); and that dont equal 3e^(-x) + xe^(-x)

Answer 11

u know some links that shows the similar example?i need to find out this answer quick

Answer 12

i forgot to do a product on the middle, but still

Answer 13

you can find it out real quick by running thru it right now, its simple enough

Answer 14

i dunno how =(

Answer 15

how did you get what you posted?

Answer 16

i use u=3+x,,differentiate got 1,and for the v,i integrate e^(-x),got -e^(-x) then (3+x) multiply with e^(-x)

Answer 17

e^-x
(3+x) -e^-x
-1 e^-x

-e^-x(3+x-1) = -e^-x (2+x) + c

id forget the usub stuff; it doesnt make the integrating simpler for this one

Answer 18

that there is a table method that follows the integration by parts

Answer 19

another way to write the answer would be:

-2e^-x -x e^-x + c

Answer 20

im off as well, musta typoed something

Answer 21

i'm still in confuse right now,,do i have to use certain formua for this kind of integration?

Answer 22

-e^-x(3+x-1) = -e^-x (2+x) + c
^
there it is, needs to be +

-e^-x(3+x+1) = -e^-x (4+x) + c

Answer 23

its just integration by parts

Answer 24

i see what you did in yours, you did by parts and i read it as a usub

Answer 25

ooo i think i should improve more on my math skills like you

Answer 26

u = 3+x v = -e^-x
du = dx dv = e^-x dx

\[\int udv=uv-\int vdu\]
\[\int (3+x)e^{-x}dx=-(3+x)e^{-x}-\int -e^{-x}dx\]
\[\int (3+x)e^{-x}dx=-(3+x)e^{-x}-e^{-x}+c\]

Answer 27

so, your concept was onteh right track, you just need to hone your skills ;)

Answer 28

he2,,so that's the final answer?you got it right? =D

Answer 29

http://www.wolframalpha.com/input/?i=derivative+-4e%5E-x+-x+e%5E-x

the wolf likes it

Answer 30

simplify as wanted

Answer 31

the wolf needs to help 'chickens' like me more