Thinking/Inquiry (10 marks) 5. Determine a quadratic function f (x) = ax2 + bx + c if its graph passes through the point (2, 19) and it has a horizontal tangent at (-1, -8). (5 marks) 6. Determine the equation of the tangent to the graph of f (x) = (x3 + 3x3 ) (-4x2+ 5) at x = 8