Solve x2 = 12x – 15 by completing the square. which is the solution set of the equation?

The answer is x = 6 + √21. The general form of quadratic function is ax2 + bx + c = 0. So, the equation x2 = 12x – 15 in the general form will be look like: x2 - 12x + 15 = 0. Now, move the number term on the right side of the equation: x2 - 12x = -15. Since b = 12, (b/2)2 = (12/2)2 = (6)2 = 36. Add this number on the both side of equation: x2 - 12x + 36 = -15 + 36. From here: (x-6)2 = 21. Take square root on both sides: x - 6 = √21. Solve for x: x = 6 + √21