Substituting for the values of a and b we get: (4−2i+7)−2(3+2i−5i)
Simplifying, we get: 4i+5
You can just assume i as a variable, because you can't really do anything with it
Substituting for the values of a and b we get: (4−2i+7)−2(3+2i−5i)
Simplifying, we get: 4i+5