7. [-l1 Points] DETAILS LARHSCALCZ 3.4.017. MY NOTES PRACTICE ANOTHER Find the point of inflection of the graph of the function. (If an answer does not exist, enter DNE.) f(x) = X\\/X + 3 (x. y) =( ) Describe the concavity. (Enter your answers using interval notation. If an answer does not exist, enter DNE.) : : concave upward concave downward 9. [-11 Points] DETAILS LARHSCALCZ 3.4.036. MY NOTES PRACTICE ANOTHER Find all relative extrema. Use the Second Derivative Test where applicable. (If an answer does not exist, enter DNE.) f(x)=x2+9X4 relative maximum (X, y) = ( ) relative minimum (X, y) = ( ) Need Help? _' 10. [-11 Points] DETAILS LARHSCALCZ 3.4.037. MY NOTES PRACTICE ANOTHER Find all relative extrema. Use the Second Derivative Test where applicable. (If an answer does not exist, enter DNE.) f(x)=x39x2+7 relative maximum (X, Y) = ( ) relative minimum (X, y) = ( ) 11. [-/1 Points] DETAILS LARHSCALC2 3.4.039. MY NOTES PRACTICE ANOTHER Find all relative extrema. Use the Second-Derivative Test when applicable. (If an answer does not exist, enter DNE.) f(x) = x4 - 4x3+ 1 relative maximum (x, y) = relative minimum (x, y) = Need Help? Read It Watch It 12. [-/1 Points] DETAILS LARHSCALC2 3.4.505.XP. MY NOTES PRACTICE ANOTHER Find a, b, c, and d such that the cubic f(x) = ax + bx2 + cx + d satisfies the given conditions. Relative maximum: (3, 23) Relative minimum: (5, 21) Inflection point: (4, 22) a= C = d=13. [I1 Points] DETAILS LARHSCALCZ 3.4.077. MY NOTES PRACTICE ANOTHER A small aircraft starts its descent from an altitude of h = % mile, 4 miles west of the runway (see figure). (a) Find the cubic f(x) = ax3 + bx2 + cx + d on the interval [4, 0] that describes a smooth glide path for the landing. (b) The function in part (a) models the glide path of the plane. When would the plane be descending at the greatest rate? X = Need Help? i 14. [/1 Points] LARHSCALCZ 3.4.079.MI. PRACTICE ANOTHER A manufacturer has determined that the total cost C of operating a factory is c = 2.5x2 + 75x + 25000, where X is the number of units produced. At what level of production will the average cost per unit be minimized? (The average cost per unit is C/X.) x = units