In equation mode, how to use - sign in the superscript.?

When I try to write the equation, B^{+}, it gives some type of error but it work B^{+a}, mean after written some letter it work properly.

+ and - are considered operators in Math. They require at least one operand.
There are two ways to use the “+” or “-” alone:

  • Use a “dummy operand” (empty braces): a^{ + { } }
  • Insert as text (quoted): a^"+"

Also can use the Unicode symbols:

  • U+207B (: superscript minus, without ^{})
  • U+02D7 (˗: modifier letter minus sign)
  • U+2010 (-: hyphen)
  • U+2011 (: non-breaking hyphen)
  • U+2012 (: figure dash)

Type U+027B or 027B and inmediatelly press Alt+X.

B^{-{}} B⁻ B^{˗} B^{‐} B^{‑} B^{‒}

Math minus superscript