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1 + 2 I + 3 I 2 1 − 2 I + 3 I 2 Equals

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Question

\[\frac{1 + 2i + 3 i^2}{1 - 2i + 3 i^2}\] equals

Options

  • i

  • -1

  • \[-\]i

  • 4

MCQ
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Solution

\[-\]i

\[\text { Let z } = \frac{1 + 2i + 3 i^2}{1 - 2i + 3 i^2}\]

\[ \Rightarrow z = \frac{1 + 2i - 3}{1 - 2i - 3}\]

\[ \Rightarrow z=\frac{- 2 + 2i}{- 2 - 2i}\times$\frac{- 2 + 2i}{- 2 + 2i}\]

\[ \Rightarrow z=\frac{\left( - 2 + 2i \right)^2}{\left( - 2 \right)^2 - \left( 2i \right)^2}\]

\[ \Rightarrow z=\frac{4 + 4 i^2 - 8i}{4 + 4}\]

\[ \Rightarrow z =\frac{4 - 4 - 8i}{8}\]

\[ \Rightarrow z=\frac{- 8i}{8}\]

\[ \Rightarrow z =-i\]

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Chapter 13: Complex Numbers - Exercise 13.6 [Page 66]

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R.D. Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.6 | Q 34 | Page 66

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