Answer:
The rocket will reach its highest point about 2.04 seconds.
Step-by-step explanation:
The function:
[tex]f(t)=-4.9t^2+20t[/tex]
Models the relationship between the height of the rocket and the time after launch t in seconds.
Since this is a quadratic function, the rocket will reach its highest point at its vertex. The vertex of a quadratic is given by:
[tex]\displaystyle \Big(-\frac{b}{2a}, f\Big(-\frac{b}{2a}\Big)\Big)[/tex]
In this case, a = -4.9, b = 20, and c = 0. Thus:
[tex]\displaystyle t=\frac{-(20)}{2(-4.9)}=\frac{10}{4.9}\approx 2.04[/tex]
The rocket reaches its maximum height after 10/4.9 or about 2.04 seconds.
Further Notes:
Then the maximum height of the rocket will be f(10/4.9):
[tex]\displaystyle f\Big(\frac{10}{4.9}\Big)=-4.9\Big(\frac{10}{4.9}\Big)^2+20\Big(\frac{10}{4.9}\Big)\approx20.41\text{ feet}[/tex]
