If we type ’49’ into a calculator and hit the square root key, the calculator calculates 7.
7*7=49
But another answer is true:
(-7) * (-7) = 49
We have the option to report the following as the answer:
When working through an algebraic derivation, is important to put in that plus minus sign when you do a square root. An example of this occurs when we do completing the square to get the quadratic formula.
Rob Sterling 