Mathematics for IGCSE & O level - Equations (Section 3 - No. 45)
In the quadratic formula, what is the role of the '±' symbol?
To indicate that the solution can be either positive or negative.
To find the solutions, there are two, possibly different, solutions.
To combine the terms under the square root.
To indicate that we must add or subtract a quantity.
Explication
The plus-or-minus symbol shows that there are typically two solutions, one obtained by addition and another by subtraction.