write a positive response to this. Add or subtract radical expressions. (6- 10i) + ( 8+5i) if a +bi and c +di are complex numbers, then their sum is (a+ bi) + ( + di)= (a +c) + (b + d)i. start by grouping like terms. (6+8) + (-10i+ 5i) combine the like terms. (6 +8) + (-10i +5i)= 14 -5i our final answer is: 14-5i