Respuesta :

y = -x2 + 5x + 36 → y = -(x2 -5x -36)


→ y =  -(x2 - 9x +4x - 36)


→ y = -[x(x-9) + 4(x - 9)]


→ y = -(x - 9)(x + 4)

Your answer would be
y=-(x-9)(x+4).