Hi I need help with questions 8 - 12 please

7:45 1 webassign.net 8. [0.67/1 Points] DETAILS PREVIOUS ANSWERS TANAPMATH7 9.6.054.NVA MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Find dy/du, du/dx, and dy/dx when y and u are defined as follows. y = > and u = vx +9 9 dy du 9 ad = dy 2x 9 ay = 2Vx ( V x + 9) Need Help? Watch It Viewing Saved Work Revert to Last Response 9. [-/1 Points] DETAILS TANAPMATH7 9.6.064.NVA MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Find an equation of the tangent line to the graph of the function at the given point. RX ) = ( * + 1); (3, 4 ) y = Need Help? Watch It 10. [-/1 Points] DETAILS TANAPMATH7 9.6.070.NVA MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER The rise of digital video and the improvement to the DVD format are some of the reasons why the average selling price of stand- alone DVD recorders has dropped in recent years. The function A(t) = 699 (t + 1)0.94 (0 s t s 13) gives the projected average selling price (in dollars) of stand-alone DVD recorders in year t, where t = 0 corresponds to the beginning of 2002.+ (Round your answers to the nearest cent.) How fast was the average selling price of stand-alone DVD recorders falling at the beginning of 2002? per year How fast was it falling at the beginning of 2013? per year Need Help? Watch It 11. [0/1 Points] DETAILS PREVIOUS ANSWERS TANAPMATH7 9.6.076.NVA MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER Government economists of a developing country determined that the purchase of imported perfume is related to a proposed "luxury tax" by the following formula where /(x) measures the percentage of normal consumption of perfume when a "luxury tax" of x% is imposed on it. N(x) = V 10,000 - 40x - 0.02x2 (0 s x s 200) Find the rate of change of N(x) for taxes of 45%, 100%, and 145%. (Round your answers to three decimal places.) 45% tax consumption/percentage increase in tax 100% tax -44 * consumption/percentage increase in tax 145% tax -45.8 X consumption/percentage increase in tax 12. [-/1 Points] DETAILS TANAPMATH7 9.6.083.NVA MY NOTES ASK YOUR TEACHER PRACTICE ANOTHER The quantity demanded per month, x, of the Zephyr tablet computer is related to the average unit price, p (in dollars), of tablet computers by the equation x = f(p) = 100 9 V 810,000 - p2 It is estimated that t months from now, the average price of a tablet computer will be given by 400 p(t) = 1 + 1 + 200 (0 s t s 60) dollars. Find the rate at which the quantity demanded per month of the tablet computers will be changing 36 months from now. (Round your answer to one decimal place.) computers/month 4