Final answer:
The midpoint between (-1+9i) and B=(5-3i) is (2+3i).
Step-by-step explanation:
The midpoint between (-1+9i) and B=(5-3i) can be found by taking the average of the real and imaginary parts separately.
For the real part, we take the average of -1 and 5 which is 2. For the imaginary part, we take the average of 9i and -3i which is 3i.
Therefore, the midpoint between (-1+9i) and B=(5-3i) is (2+3i).