Question

Find the integral of x(6x+7)^8 dx

Answer 1

integral by subs, let u = 6x+7

Answer 2

Yes I tried that but nothing canceled out

Answer 3

because du/dx would equal to 6

Answer 4

u = 6x+7 ---------> x=(u-7)/6, right ?
du=6dx or
dx = 1/6 * du
now, plug of them to the original problem

Answer 5

oh I see. I got dx=6du instead of 1/6 du

Answer 6

btw, u were missing dx above :)

Answer 7

haha thanks, i'll add it in

Answer 8

welcome

Answer 9

so now I got integral of (u-7)(u^8) du. Is that right?

Answer 10

where's 1/6 ?

Answer 11

oops I meant integral of [ (u-7)/36 ] (u^8) du

Answer 12

so its 1/36 integral of (u-7)(u^8) du

Answer 13

ok...

Answer 14

Still can't integrate

Answer 15

use distributive property to simplies (u-7)u^8 = u^9 - 7u^8

Answer 16

just integrate it one by one

Answer 17

\[\int\limits x(6x+7)^8 dx\]\[u=6x+7\]\[{du \over 6}=dx\]\[x={u-7 \over 6}\]\[\int\limits {u-7 \over 6}u^8{du \over 6}\]\[\int\limits {u^9-7u^8 \over 36}du\]\[{1 \over 36}\int\limits u^9-7u^8 \space du\]I'll let you finish

Answer 18

Thanks got my answer. [ (6x+7)^10 /360 ] - [ 7(6x+7)^9 /324]

Answer 19

yeah, correct

Answer 20

dont forget + c :p

Answer 21

This was a tricky one.. :o thanks for sticking by lol