To use the x-intercept method to find the solutions of the equation x³ + 8x² + 9x + 18 = 0, we need to factor the equation, set each factor to zero, and solve for x. One possible way to do this is:
x³ + 8x² + 9x + 18 = 0
(x + 2)(x² + 6x + 9) = 0 (by factoring out a common factor of (x + 2))
(x + 2)(x + 3)(x + 3) = 0 (by factoring the quadratic trinomial x² + 6x + 9)
Therefore, the solutions of the equation are x = -2 (with multiplicity 1) and x = -3 (with multiplicity 2). Thus, the correct answer is d. x = -1, 3, or -6.