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Express the Following Complex Number in the Standard Form a + I B: ( 1 + 2 I ) − 3

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प्रश्न

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

\[(1 + 2i )^{- 3}\]

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उत्तर

\[( 1 + 2i )^{- 3} \]

\[ = \frac{1}{\left( 1 + 2i \right)^3}\]

\[ = \frac{1}{1 + 8 i^3 + 6i + 12 i^2}\]

\[ = \frac{1}{1 - 8i + 6i - 12} \left( \because i^2 = - 1 \text { & }  i^3 = - i \right)\]

\[ = \frac{1}{- 2i - 11}\]

\[ = \frac{1}{- 2i - 11} \times \frac{- 2i + 11}{- 2i + 11}\]

\[ = \frac{- 2i + 11}{4 i^2 - 121}\]

\[ = \frac{- 2i + 11}{- 4 - 121}\]

\[ = \frac{- 2i + 11}{- 125}\]

\[ = - \frac{11}{125} + \frac{2i}{125}\]

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अध्याय 13: Complex Numbers - Exercise 13.2 [पृष्ठ ३१]

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आर.डी. शर्मा Mathematics [English] Class 11
अध्याय 13 Complex Numbers
Exercise 13.2 | Q 1.09 | पृष्ठ ३१

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