A bullet is fired straight upward with an initial speed of 720 ft/s. It’s path is modeled by the equation h=-16t^2 + 720t, where h is the height of the bullet t seconds after it was fired. When does the bullet reach a height of 4,000 feet?

The bullet reaches a height of 4000 feet after 6.49 seconds, and then, coming back down, after 38.5 seconds.

Step-by-step explanation:

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

.

This polynomial has roots such that , given by the following formulas:

The height of the bullet after t seconds is given by:

When does the bullet reach a height of 4,000 feet?

This is t for which . So

Dividing by 16

So

The bullet reaches a height of 4000 feet after 6.49 seconds, and then, coming back down, after 38.5 seconds.

1.5%

step-by-step explanation:

1/4 and 8/3 because:

the reciprocal if 4 is 1/4 because 4 is used as 4/1 and the opposite of that is 1/4. the opposite of 3/8 is 8/3 so that is the answer.