Answer:
y = -(x+4)² +7
Step-by-step explanation:
I find it convenient to factor the leading minus sign from the first two terms, then work with what's left.
... y = -(x² +8x) -9
Now, add the square of half the x-coefficient inside parentheses. Add the opposite of that amount outside parentheses.
... y = -(x² +8x +4²) -9 +4²
... y = -(x +4)² +7 . . . . . . . . . rewrite parentheses as a square; collect terms
