For Exercises 40–46,

a. List all possible rational roots or rational zeros.

b. Use Descartes’s Rule of Signs to determine the possible number of positive and negative real roots or real zeros.

c. Use synthetic division to test the possible rational roots or zeros and find an actual root or zero.

d. Use the quotient from part (c) to find all the remaining roots or zeros.

x⁴ - x³ - 7x² + x + 6 = 0