The symbol ± is read as ‘plus or minus’ and denotes the two possibilities of  +  and−as in the the quadratic formula, when either the positive or negative square root of the discriminant is valid. It can be efficiently used alongside the ∓ symbol, read ‘minus or plus’, as in the identity
  to signify that the  +  (respectively − ) in ± corresponds to the − (respectively  + ) in ∓.