I'll guess the answer is <em>you can tell that pi is an irrational because it has a </em>non-terminating yet non-repeating decimal representation.<em>
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Of course it's not clear how we tell this. We can't know for sure just by looking at the first trillion digits we've figured out whether it repeats or not. Someone told us it didn't, that's really how we know.

Using the quadratic formula we get

Therefore the tennis ball is at least 15 feet above the ground from 0.5 seconds to 2.04 seconds
Answer step-by-step explanation:
We know that the critical t value for a 98% confidence level for a sample of size n = 18:
Finding degrees of freedom (n-1) = 17
-search the information in table t for 0.98 and find that t = 2.567