The roots of the quadratic equation z^2 + az + b = 0 are -7 + 2i and -7 - 2i. What is a+b?

What could explain what happened when the time was equal to 120 minutes

The holiday party will cost $160 if 8 people attend. if there are 40 people who attend the party, how much will the holiday party cost

An automobile assembly line operation has a scheduled mean completion time, μ, of 12 minutes. the standard deviation of completion times is 1.6 minutes. it is claimed that, under new management, the mean completion time has decreased. to test this claim, a random sample of 33 completion times under new management was taken. the sample had a mean of 11.2 minutes. assume that the population is normally distributed. can we support, at the 0.05 level of significance, the claim that the mean completion time has decreased under new management? assume that the standard deviation of completion times has not changed.