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Mathematics 18 Online
OpenStudy (anonymous):

i need help solving integral e ^sqrt(x)/sqrt(x) with u substitution

OpenStudy (amistre64):

id assume the most obvious sub is u=sqrtx

OpenStudy (amistre64):

you should end up with 2u' e^u

OpenStudy (anonymous):

can you pls show me how u got that

OpenStudy (amistre64):

how "I" got it? or how youre spose to get it?

OpenStudy (amistre64):

i got it by looking at the setup and realizing what i needed to do to make it uable

OpenStudy (anonymous):

i mean i got du=1/2x-1/2

OpenStudy (anonymous):

although i dont remember what to do next

OpenStudy (anonymous):

1/2x^-1/2

OpenStudy (amistre64):

u = sqrtx du = 1/2sqrtx dx 2sqrtx du = dx now substitute it in;

OpenStudy (anonymous):

thats the part that confuses me

OpenStudy (amistre64):

everywhere you see a sqrtx; put a u ; since u = sqrtx

OpenStudy (amistre64):

everywhere you see a dx, replace it with 2sqrtx du since 2sqrtx du = dx

OpenStudy (amistre64):

your simply replacing parts to clean up the scene

OpenStudy (anonymous):

oh right

OpenStudy (anonymous):

can you show me how u differentiated them

OpenStudy (anonymous):

like how u wrote the origninal ones

OpenStudy (anonymous):

i made it e^sqrt(x)*x^1/2

OpenStudy (amistre64):

let u = sqrtx ; then deriva both sides du = 1/2sqrtx dx as per the rules of derivatives ; rearrange so dx i all alone

OpenStudy (amistre64):

when you bring somethng over the fraction bar, you negate the exponents

OpenStudy (anonymous):

oh ya

OpenStudy (amistre64):

2sqrtx du = dx ; but u = sqrtx 2u du = dx

OpenStudy (amistre64):

e^sqrtx/sqrtx dx replace parts e^u/u 2u du clean up 2e^u du

OpenStudy (anonymous):

ok so i got integral of e^u *sqrt(x)-1/2 times dx which =2*sqrtx

OpenStudy (anonymous):

where do i put 2sqrt x?

OpenStudy (amistre64):

dx = 2sqrtx du replace it all or you can see it as dx ---- = 2 du sqrtx

OpenStudy (anonymous):

ook thanks i think i get it little more now

OpenStudy (amistre64):

just keep at it; pull it all apart and replace all the things you can replace

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