Solve the following problems: 1. Determine the values of x where a curve y = x3 - 3x - 9x + 12 has horizontal tangent lines. Bataan is known for its mountains and trails such as the Dambana ng Kagitingan and Duhat Trail which are ideal for history and nature lovers. The slopes of the hills in Duhat trail represent a curve. (Photo credits: Bataan Weather Page) 2. Aside from mountain ranges and trails, Bataan is known for its beautiful beaches. While beach in Barangay Paysawin, Bogoc, Baloan 24 A tourist threw a pebble in the sea, causing water ripples. The shape formed were circles increasing in area. The formula for finding the area of a circle is given by A = ar?. a. Find the average rate at which the area of a circle changes with r as the radius increases from 2 to 4 units. b. Solve for the instantaneous rate at which the area changes with r, when r - 5