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Evaluate: [i18+(1i)25]3

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Question

Evaluate: `[i^18 + (1/i)^25]^3`

Sum
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Solution

`[i^18 + (1/i)^25]^3`

= `[(i^2)^9 +  1 /((i^2)^12 i)]^3`

= ` [(-1)^9 +  1 /((-1)^12 i)]^3`

= `[ -1  + 1/i  xx  i/i]^3`

= `[- 1 -i]^3`

= `-(1 + i)^3`

Now, `[ (a + b)^3 = [a^3 + 3a^2b + 3ab^2 + b^3]`

= – (1 + 3i + 3i2 + i2)

= – (1 + 3i - 3 + i2.i)

= (– 2 + 3i – i)

= – (– 2 + 2i)

= 2 – 2i

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Chapter 4: Complex Numbers and Quadratic Equations - Miscellaneous Exercise [Page 85]

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NCERT Mathematics [English] Class 11
Chapter 4 Complex Numbers and Quadratic Equations
Miscellaneous Exercise | Q 1. | Page 85

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