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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: i(4+3i)(1-i)

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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:

`("i"(4 + 3"i"))/((1 - "i"))`

Sum
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Solution

`("i"(4 + 3"i"))/((1 - "i")) = (4"i" + 3"i"^2)/(1 - "i")`

= `(4"i" - 3)/(1 - "i")`  ...[∵ i2 = – 1]

= `(4"i" - 3)/(1 - "i") xx (1 + "i")/(1 + "i")`

= `(4"i" + 4"i"^2 - 3 - 3"i")/(1 - "i"^2)` 

= `(4"i" - 4 - 3 -3"i")/(1 + 1)`   ...[∵ i2 = – 1]

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

= `(-7)/2 + 1/2"i"`

This is of the form a + bi, where a = `(-7)/2` and b = `1/2`.

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

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