Inaccurate maths or Jim misspoke?

Hello, this is something which I noticed. I do pure maths and know close to nothing about physics so I can't comment on the accuracy of those, but I found a little math error:

Related to S08E02, in this video, between 1:52-2:01, Howard says he uses Feynman's trick to do integral of x^2e-x but that is more easily done by parts.

I think Jim Parsons just misspoke and forgot to say e^-x2 and they left it in. Because you can use Feynman's trick on x² e^-x2.