Answer: time to reach maximum height = 605
Explanation:
The expression that relates height with time is
M(d)=-0.123x^2+148.83x-21.07
Where time = x
d = height
The expression is a quadratic equation. If height of the object is plotted against time, the resulting graph is a parabola whose vertex is equal to the maximum height attained by the object. The time, x corresponding to the vertex is the time for it to reach maximum height.
To find x,
x = -b/2a
Where a= 0.123
b = 148.83
x = - 148.83 / -2 × -0.123
x = -148.83 / -0.246
= 605
Substituting x = 605 in the equation,
M(d)=-0.123x^2+148.83x-21.07
d = -0.123 × 605^2 + 148.83×605
= - 45021.075+ 90042.15
= 45020.4
Approximately 45000 feet