K Solve the following equation by making an appropriate substitution. 5 5 6 x -2x +1=0 Make an appropriate substitution and rewrite the equation in quadratic form. Let u= , then the quadratic equation in u is Solve the equation. Select the correct choice below and, if necessary, fill in the answer box to complete your choice. OA. The solution set (Type an integer or a simplified fraction. Use a comma to separate answers as needed.) OB. The solution set is the empty set.