Algebra II

Question

If a rocket is propelled upward from the ground at 98 m/sec, its height after t seconds is given by h = -4.9t² + 98t. During what interval of time will the rocket be higher than 445.9 m?
Question 15 options:

1) (7, 12)

2) (8, 12)

3) (7, 13)

4) (6, 13)

Answer 1

Program the polynomial into a graphing calculator: -4.9t² + 98t - 445.9  which is variable height minus the stated threshhold.  Find the zeros of this function.  They are 7 & 13.  Since the graph is a downward-opening parabola, it follows that the height above the 445.9 level occurs between 7 and 13 seconds.