+ The vertex of this parabola is at (4, -3), that means we have the equation of this parabola: y=a(x-4)² -3
+ when the x-value is 5, the y-value is -6, we have -6=a(5-4)² -3
or we have a= -6+3, and we have a= -3
+ what is the coefficient of the squared term in the parabola's equation, that is a, and a= -3