Please help me it’s 2 questions and I need real answers If you don’t now don’t answer question 9 and 10

Which value is not a solution of 8x^3 – 1 = 0

Aproduction manager test 10 toothbrushes and finds that their mean lifetime is 450 hours. she then design sales package of this type of toothbrush. it states that the customers can expect the toothbrush to last approximately 460 hours. this is an example of what phase of inferential statistics

The longer leg of a 30-60-90 trangle is 18