How do we use complex conjugates to divide imaginary numbers?

The conjugate of an expression is you basically changing the operation. For example the conjugate of 4x+3i would be 4x-3i. Now when dividing imaginary numbers using complex conjugates you would take the conjugate of the denominator and multiply the top and bottom by it. The rest is simple you would foil both the top and bottom but when you get to your final answer you would express it in a+bi form. So for example if you get an answer that is 1 take away 21i over 13  you would simplify further and your final answer would be 1 over 13 take away 21 over 13i.