Something's wrong...could someone please check my work? Attachments to come...

Question

poofypenguin · Answer

Here's the question:

poofypenguin · Answer

Here's the work that I've done:

poofypenguin · Answer

Only one of the part's is wrong, but I'm not sure which one or what I did wrong...

poofypenguin · Answer

Could anyone help me?

anonymous · Answer

Yes I am checking it.

poofypenguin · Answer

Thanks so much! I've been waiting all night! :D

anonymous · Answer

There will be -40x^3 ? Last one

anonymous · Answer

instead of -800x^6 there may be -40x^3

anonymous · Answer

@PoofyPenguin What do you think? I am rechecking my soln ... wait for 5 min.

poofypenguin · Answer

I think that I made the mistake in that area but what about the 20x^3?

anonymous · Answer

Yes...

anonymous · Answer

attachment

anonymous · Answer

mistake is here

anonymous · Answer

@PoofyPenguin

poofypenguin · Answer

Let me give it a try.

poofypenguin · Answer

Yep! That was correct! Could you please explain what I did wrong? Where did the 20x^3 go?

anonymous · Answer

anonymous · Answer

You wrote $$\large{-40x^3}$$ instead of -2 ... and that is the MISTAKE.

poofypenguin · Answer

Alright! I see it now! Thanks so much for all of your help! :D

anonymous · Answer

No problem.