I am typing the equation with \textbackslash inside as follows. It displays error "underfined control sequence". Can anyone explain me what the problem is? Thanks.

Here $x\in [0,\infty]^n$ \textblackslash  $\{1\}$. I got error "Undefined control sequence.

Here a \textbackslash b. This line is OK.

1 Answer 1


you have


"black" should be "back". A simple typo.

  • oh, why i didn't recognize it. The error message of latex doesn't give me any hint. Thanks a lot friend! Jan 10, 2014 at 17:46

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.