Answer:
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When the cannonball lands the height h is zero.
Set the value of the function as zero and solve for t:
- -4.9t² + 24.5t + 9.8 = 0
- t² - 5t - 2 = 0
- t = (5 ± √(5² + 8))/2
- t = (5 ± √33)/2
- t = (5 - √33)/2 or t = (5 + √33)/2
- t = - 0.4 or t = 5.4 (rounded)
The greater value of t represents the time we need.