Factor u⁴+7u²-8 honestly I'm just confused how to solve ;-; I see the answer is (u-1)(u-1)(u²+8) but I'm not sure how to show the work.

Monitors manufactured by tsi electronics have life spans that have a normal distribution with a standard deviation of 1800 hours and a mean life span of 20,000 hours. if a monitor is selected at random, find the probability that the life span of the monitor will be more than 17,659 hours. round your answer to four decimal places.