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What is the real part of (9 + 3i)^2?(a) 81(b) 90(c) 54(d) 72The question was asked in an online quiz.My question is taken from Binomial Theorem for Positive Integral Index in portion Binomial Theorem of Mathematics – Class 11

Answer»

The correct CHOICE is (d) 72

Easy EXPLANATION: Using BINOMIAL THEOREM (9 + 3I)^2 = 81 + 54i + 9i^2

We know that i^2 = –1

Therefore, (9 + 3i)^2 = 81 + 54i – 9

(9 + 3i)^2 = 72 + 54i

Real part = 72.



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