Respuesta :
that symbol represents "plus out minus". usually represents uncertainty if it is beside a number.
e.g. 3± 0.3 means that the actual answer lies between 2.7 and 3.3
e.g. 3± 0.3 means that the actual answer lies between 2.7 and 3.3
Plus over minus has multiple meaning, it generally indicates a choice of exactly two possible values one of which is the negation of the other.