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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: 4i8-3i9+33i11-4i10-2

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Question

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

`(4"i"^8 - 3"i"^9 + 3)/(3"i"^11 - 4"i"^10 - 2)`

Sum
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Solution

i8 = (i2)4 = (–1)4 = 1

i9 = i8 × i = (i2)4i = (– 1)4i = i

i11 = i10 × i = (i2)5i = (– 1)5i = – i

i10 = (i2)5 = (– 1)5 = – 1

∴ `(4"i"^8 - 3"i"^9 + 3)/(3"i"^11 - 4"i"^10 - 2) = (4(1) - 3"i" + 3)/(3(-"i") - 4(-1) - 2)`

= `(4 - 3"i" + 3)/(-3"i" + 4 - 2)`

= `(7 - 3"i")/(2 - 3"i")`

= `(7 - 3"i")/(2 - 3"i") xx (2 + 3"i")/(2 + 3"i")`

= `(14 + 21"i" - 6"i" - 9"i"^2)/(4 - 9"i"^2)`

= `(14 + 15"i" + 9)/(4 + 9)`   ...[∵ i2 = – 1]

= `(23 + 15"i")/13`

= `23/13 + 15/13"i"`

This is of the form a + bi, where a = `23/13` and b = `15/13`.

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Chapter 1: Complex Numbers - Exercise 1.1 [Page 6]

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