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Express the following in the form of a + ib, a, b∈R i = −1. State the values of a and b: (1 + i)−3

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प्रश्न

Express the following in the form of a + ib, a, b∈R i = `sqrt(−1)`. State the values of a and b:

(1 + i)−3 

बेरीज
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उत्तर

(1 + i)−3  = `1/((1 + "i")^3`

= `1/(1 + 3"i" + 3"i"^2 + "i"^3)`

= `1/(1 + 3"i" - 3 - "i")`   ...[∵  i2 = – 1, i3 = – i]

= `1/(-2 + 2"i")`

= `1/(-2 + 2"i") xx (-2 - 2"i")/(-2 - 2"i")`

= `(-2 - 2"i")/(4 - 4"i"^2)`

= `(-2 - 2"i")/(4 + 4)`   ...[∵  i2 = – 1]

= `(-2 -2"i")/8`

= `-1/4 - 1/4 "i"`

This is of the form a + bi, where a = `-1/4` and b = `-1/4`

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पाठ 1: Complex Numbers - Exercise 1.1 [पृष्ठ ६]

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