Exercise Using proportional parametric representation, obtain the polynomial passing by points A(-2,1), B(2,3), C(3,1) and D(1,-1). a) Write the equation or equations passing by the 4 points. How many equations do you need? What is the order of each equation? What are the unknown variables? b) What is the parameter value at points A, B, C and D? c) Write the equation system or systems which will allow you to calculate the unknown variables. d) Define the parametric equation of the polynomial which passes through points A to D. Plot the polynomial. e) Explain the plot. f) What are your conclusions?