Answer:
{6-√21, 6+√21}
Step-by-step explanation:
It usually works well to put the x-terms on one side of the equal sign. Then add the square of half the x-term coefficient.
x^2 -12x = -15 . . . . . . subtract 12x
The x-term coefficient is -12, so the square of half that is (-12/2)^2 = 36. Adding 36, we have ...
x^2 -12x +36 = -15 +36
(x -6)^2 = 21
x -6 = ±√21 . . . . . take the square root
x = 6 ±√21 . . . . . add 6
The solution set is ...
{6-√21, 6+√21}
