Skills Handbook - Squaring Numbers and Finding Square Roots - Exercises - Page 889: 14

$a=3\text{ or }a=-3$

To solve the equation $a^2=9$, we must perform the opposite operation of squaring, which is taking the square root, in order to clear the exponent: $$a^2=9$$$$\sqrt {a^2}=\sqrt {9}$$$$a=\pm3$$$$a=3\text{ or }a=-3$$