When you trace the graph of a function on your calculator to find the value of an x-intercept, you often see the y-value jump from positive to negative when you pass over the zero. By using smaller windows, you can find increasingly more accurate approximations for x. This process can be automated by your calculator. The automation uses successive midpoints of each region above and below zero; it is called the bisection method. Approximate the x-intercepts for each equation by using the program BISECTN, then use synthetic or long division to find any nonreal zeros. [See Calculator Note 7I for the BISECTN program.]
a. y = x5 - x4 - 16x + 16
b. y = 2x3 + 15x2 + 6x - 6
c. y = 0.2(x - 12)5 - 6(x - 12)3 - (x - 12)2 + 1
d. y = 2x4 + 2x3 - 14x2 - 9x - 12