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Mathematics 8 Online
OpenStudy (anonymous):

kjlhjkhlkj

OpenStudy (anonymous):

@jim_thompson5910 @iambatman

OpenStudy (freckles):

Find the first few derivatives and observe a pattern to find nth derivative of g

OpenStudy (freckles):

I think I would write as a product for fun \[g(x)=xe^{-x}\] then differentiate

OpenStudy (anonymous):

1st:e^-x-xe^-x 2nd:e^-x-2xe^-x 3rd:3e^-x-xe^-x

OpenStudy (anonymous):

it has something to do with -1(x-n) right?

OpenStudy (anonymous):

with an exponent

OpenStudy (freckles):

\[g^{(1)}(x)=1e^{-x}-xe^{-x} \\ g^{(2)}(x)=-2e^{-x}+xe^{-x}=(-1)(2e^{-x}-xe^{-x}) \\ g^{(3)}(x)=3e^{-x}-xe^{-x}\]

OpenStudy (freckles):

Do you notice it is alternating

OpenStudy (freckles):

also the part in front of e^{-x} is the number of the n-th derivative

OpenStudy (freckles):

like what i mean is : the 1st derivative we have a 1 in front of e^{-x} the 2nd derivative we have a 2 in front of e^{-x} and so on...

OpenStudy (anonymous):

so its e^(-nx)?

OpenStudy (freckles):

nothing is changing in the exponent area

OpenStudy (anonymous):

ok

OpenStudy (freckles):

by the pattern above i can say the 4th derivative would be \[g^{(4)}=(-1)(4e^{-x}-xe^{-x})\]

OpenStudy (freckles):

the 5-th derivative would be \[g^{(5)}=5e^{-x}-xe^{-x}\]

OpenStudy (freckles):

so can you take a guess at what the n-th derivative would look like

OpenStudy (anonymous):

not yet. it has something to do with even and odd functions though

OpenStudy (freckles):

\[g^{(1)}(x)=(-1)^{1+1}(1e^{-x}-xe^{-x}) \\ g^{(2)}(x)=(-1)^{2+1}(2e^{-x}-xe^{-x}) \\ g^{(3)}(x)=(-1)^{3+1}(3e^{-x}-xe^{-x}) \\ g^{(4)}(x)=(-1)^{4+1}(4e^{-x}-xe^{-x})\]

OpenStudy (anonymous):

g^(n)(x)=(-1)^(n+1)(e^(-x)-xe^(-x))

OpenStudy (freckles):

what about the number in front of e^(-x)?

OpenStudy (anonymous):

ne^(-x)

OpenStudy (freckles):

ok

OpenStudy (anonymous):

thank you so much

OpenStudy (freckles):

\[g^{(n)}(x)=(-1)^{n+1}(n e^{-x}-xe^{-x})\]

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