HELP PLEASE 20 POINTS

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)

Which of the following is the major negative aspect of crossover designs for research studies? a. prohibitive cost b. residual effects c-subject drepout d. incomplete randomization e. large sample size required

The table below shows the number of free throw shots attempted and the number of shots made for the five starting players on the basketball team during practice. each player's goal is to make 80% of her shots. players number of free throws made free throw attempts kelly 16 20 sarah 25 30 maggie 31 40 liz 44 50 kim 47 60 how many players made at least 80% of their shots? round to the nearest percent.