ant z Solve the following equation by making an appropriate substitution. x -2 - 3x 1 - 18=0 Make an appropriate substitution and rewrite the equation in quadratic form. Let u = x , then the quadratic equation in u is u2- 3u - 18=0 Solve the equation. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. A. The solution set is (Simplify your answer. Use a comma to separate answers as needed.) O B. The solution set is the empty set