Question 1201821
-3(x - 3)^2 + 108 First FOIL (x - 3)(x - 3) = x^2 - 6x + 9
Then -3(x^2 - 6x + 9) + 108 Distribute the -3
-3x^2 + 18x - 27 + 108 Now combine the like terms.
-27 + 108 = 81  This is the y-intercept, so this is where the plane takes off.  It is the initial height.
What is the height of the hovercraft at the time of takeoff?  81 meters.  You could have also graphed it on Desmos.com and solved it as well.