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Evaluate the Following: X 4 + 4 X 3 + 6 X 2 + 4 X + 9 , When X = − 1 + I √ 2

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प्रश्न

Evaluate the following:

\[x^4 + 4 x^3 + 6 x^2 + 4x + 9, \text { when } x = - 1 + i\sqrt{2}\]

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उत्तर

\[ x = - 1 + \sqrt{2}i\]

\[ \Rightarrow x^2 = \left( - 1 + \sqrt{2}i \right)^2 \]

\[ = 1 + 2 i^2 - 2\sqrt{2}i\]

\[ = - 1 - 2\sqrt{2}i\]

\[ \Rightarrow x^3 = \left( - 1 - 2\sqrt{2}i \right) \times \left( - 1 + \sqrt{2}i \right)\]

\[ = 1 - \sqrt{2}i + 2\sqrt{2}i - 4 i^2 \]

\[ = 5 + \sqrt{2}i\]

\[ \Rightarrow x^4 = \left( - 1 - 2\sqrt{2}i \right)^2 \]

\[ = 1 + 8 i^2 + 4\sqrt{2}i\]

\[ = - 7 + 4\sqrt{2}i\]

\[ \Rightarrow x^4 + 4 x^3 + 6 x^2 + 4x + 9 = - 7 + 4\sqrt{2}i + 4\left( 5 + \sqrt{2}i \right) + 6\left( - 1 - 2\sqrt{2}i \right) + 4\left( - 1 + \sqrt{2}i \right) + 9\]

\[ = - 7 + 4\sqrt{2}i + 20 + 4\sqrt{2}i - 6 - 12\sqrt{2}i - 4 + 4\sqrt{2}i + 9\]

\[ = 12\]

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अध्याय 13: Complex Numbers - Exercise 13.2 [पृष्ठ ३२]

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आर.डी. शर्मा Mathematics [English] Class 11
अध्याय 13 Complex Numbers
Exercise 13.2 | Q 16.3 | पृष्ठ ३२

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