Question

How the do you integrate this? :s help pls

Answer 1

\[\int\limits_{}^{}te^{-4t}dt\]

Answer 2

usub I think

Answer 3

integrate by parts

Answer 4

Should I pick t as my U?

Answer 5

There's only really two options... if you can't tell which to pick, try whichever, if the integral gets more complex, then you chose wrong. You'll eventually be able to tell which to pick as u.

Answer 6

Can you solve this with u-sub?

Answer 7

Don't see how. By parts isn't hard anyway

Answer 8

u= t
du= dt
dv= e^-4t

v=-1/4 s^-4t

Answer 9

\[v=- \frac{ 1 }{ 4 }e^{-4t}\]

Answer 10

right?

Answer 11

Yes

Answer 12

\[-\frac{ t }{ 4e^{-4t} }+\frac{ 1 }{ 4 }\int\limits_{}^{}e^{-4t}\]

Answer 13

That first term, no

Answer 14

meh ohh

Answer 15

\[-\frac{ te^{-4t} }{ 4 }+\frac{ 1 }{ 16 }e^{-4t}\]

Answer 16

Second term should be negative

Answer 17

why, v is negative so

Answer 18

Because check your integration

Answer 19

1/4 divided by -4

Answer 20

wait, is my v correct?

Answer 21

Yes just after your integration here, the second term should be negative \[\large -\frac{ t }{ 4e^{-4t} }+\frac{ 1 }{ 4 }\int\limits\limits_{}^{}e^{-4t}\]

Answer 22

After integrating that

Answer 23

\[-\frac{ te^{-4t} }{ 4 }--\frac{ 1 }{ 4 }\int\limits_{}^{}e^{-4t}\]

Answer 24

No, up until that point was fine. It was AFTER integrating that.

Answer 25

ohhhh hehe

Answer 26

ok I just need to change the sign then :)

Answer 27

thank you

Answer 28

You're welcome