ISRO 2011-ECE : Complex Numbers

Question

(3 + i)/(5 + 5i)  is same as

a. (2 - i)/5

b. 3 - i

c. 5 - 5i

d. (2 + i)/5

Answer 1

Multiply denominator and numerator by (5 - 5i), the process is called rationalization in mathematics. Remember i _* i = (-1).

Denominator changes to form of a²-b² i.e 50. Numerator is (20 - 10i).

Solving further, we get Option (a).