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Express the Following Complex Number in the Standard Form a + I B: ( 1 + I ) ( 1 + 2 I )

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Question

Express the following complex number in the standard form a + i b:

\[(1 + i)(1 + 2i)\]

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Solution

\[ \left( 1 + i \right) \left( 1 + 2i \right)\]

\[ = 1 + 2i + i + 2 i^2 \]

\[ = 1 + 3i - 2 \left( \because i^2 = - 1 \right)\]

\[ = - 1 + 3i\]

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Chapter 13: Complex Numbers - Exercise 13.2 [Page 31]

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R.D. Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.2 | Q 1.01 | Page 31

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