Caroline rewrote a quadratic equation in vertex form by completing the square, but her work has errors.
f(x)
-2x² + 12x15
-2(x² - 6x) — 15
-2(x² - 6x + 9) - 9 - 15
-2(x - 3)²9 - 15
-2(x - 3)² - 24
Identify the first error in her work.