.
They instruct you that your formula is
h(x) = .
I forget about this "graphing utility" which is mentioned in the text, since I don't know what is they are talking about,
and, probably, I do not have it at all (thanks to god).
I will show you how to calculate it directly by hand.
Simply substitute the value of 80 into the formula and calculate:
h(x) = 80 = .
Now you need to find x from this equation
80 = .
For it, multiply both sides by 150^2 = 22500. You will get
80*22500 = -32x^2 + 22500x, or, equivalently,
32x^2 - 22500x + 1800000 = 0.
Apply the quadratic formula
= = .
= = 92;
= = 611.
Answer. There are two solutions: 92 ft and 611 ft (approximately).
Plot y = (red) and y = 80 (green)