Answer
Fill the blank with:
factoring and using the zero product principle.
Work Step by Step
This does not have the form to directly apply the square root principle.
We would then perhaps, try to factor:
search for factors of 15 whose sum is 8 ... and find 5 and 3.
So, the initial equation is equivalent to
$(x+5)(x+3)=0$
Using the zero product principle, we find the solution set to be
$\{-5, -3\}$
Fill the blank with:
factoring and using the zero product principle.
