Sketching the Graph of a Polynomial Function In Exercises 69-82, sketch the graph of the function by (a) applying the Leading Coefficient Test, (b) finding the real zeros of the polynomial, (c) plotting sufficient solution points, and (d) drawing a continuous curve through the points. 75. f(x) = 3x3 - 15x2+ 18x # 76. f(x) = -4x3 + 4x2+ 15x $ 77. f(x) =-5x2-13 # 78. f(x) = -48x2+ 3.14