Answer
See 4 part explanation below
Work Step by Step
A) To add complex numbers we add the real parts and imaginary parts separately.
B) Multiplying is like expanding binomial expressions, and substituting $i^2=-1$
$(2+5I)(2-i)=10i-3i-5*i^2+6 = =(10-3)i-5*(-1)+6 = 11+7i$
C) Yes as the expression becomes $9-i^2 = 10$
D) Multiply the numerator and denominator by $3+i$ which is the conjugate of the denominator.
