# A rocket fired into the air is modeled by the function #h(t)=-16t^2 + 160t#. How many seconds is the rocket in the air?

##### 2 Answers

The rocket will be in the air for

#### Explanation:

We have to find out the positive values of

We can do it algebraicly:

Since the coefficient next to

We can also solve this task using graph of the function:

graph{-16x^2+160x [-50, 50,-20, 428]}

From this graph we clearly see, that the height is not lower than zero for

#### Explanation:

Given is

It has not been explicitly given but it is presumed that

Clearly the rocket will be in air between the time interval from

Setting the height

Factorizing we obtain

We have two values of

- from first factor

#t=0# - from second factor

#(t-10)=0#

#=> t=10#

We obtain

**Graphically**

graph{y=-16x^2+160x [-5, 15,-15, 428]}

height

We obtain time of flight as