Can someone please check me (to make sure my reasoning is sound, primarily...but always nice to have the algebra looked at as well)?

d/dx [(x-2) d/dx (5-x4)]

=d/dx [(x-2)(-4x^3)]

=d/dx [-4x^4 + 8x^3]

= -16x^3 + 24x^2

Question

Can someone please check me (to make sure my reasoning is sound, primarily...but always nice to have the algebra looked at as well)?

d/dx [(x-2) d/dx (5-x4)]

=d/dx [(x-2)(-4x^3)]

=d/dx [-4x^4 + 8x^3]

= -16x^3 + 24x^2

anonymous · Answer

that should read d/dx (5-x^4) up top

anonymous · Answer

rather than (5-x4)

anonymous · Answer

look ok

kainui · Answer

Looks correct to me. A helpful tool to use is www.wolframalpha.com

anonymous · Answer

Thanks.  When I can put this kind of query into wolframalpha I do, but it didn't like the syntax on this one.

kainui · Answer

Try breaking it up and just doing one derivative at a time. =)

anonymous · Answer

You're too right, but I wasn't sure it would be ok to do...now I am the wiser, and I thank you.

anonymous · Answer

yw