Question

Help please.!

Answer 1

u,du,a,b are correct

Answer 2

how you got that f(u)
f(u) is much simpler...

Answer 3

Yes, The last two problems,

Answer 4

remember that 1+3x^4 changes to u
so, (1+3x^4)^2 will be just u^2, right ?

Answer 5

just u^2?

Answer 6

f(u) is not just u^2
(1+3x^4)^2 will be just u^2

Answer 7

oh, I got it.

Answer 8

what you got f(u) as ?

Answer 9

(12x^3)^2

Answer 10

*sigh*
f(u) is the function of u only...

Answer 11

(1+3x^4)^2?

Answer 12

(1+3x^4)^2 = u^2
(1+3x^4)^2 * (x^3dx) = u^2 (du/12)
because
du = 12 x^3 dx

Answer 13

I see

Answer 14

so f(u) = (1/12) u^2

Answer 15

Thats cool!

Answer 16

:)

Answer 17

what is The value of the original integral ?
i dont get this defition...

Answer 18

you just solve
\(\large (1/12)\int \limits_{49}^{769}u^2du=....?\)
can you ?

Answer 19

\[\frac{ 1 }{ 12 }*\frac{ 1 }{ 3 \int\limits_}^{?}\]

Answer 20

\[\frac{ 1 }{ 12 }\frac{ 1 }{ 3 } \int\limits_{49}^{769} u^3du\]

Answer 21

you already integrated, du won't come
(1/12) * (1/3) * [u^3] from 49 to 769

Answer 22

(1/12) * (1/3) * [u^3] from 49 to 769 = (1/12) * (1/3) * [769^3-49^3] =.. ?

Answer 23

12628860?

Answer 24

yes. i get the same.