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Express the following complex number in the standard form a + i b: (11−4i−21+i)(3−4i5+i) - Mathematics

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Question

Express the following complex number in the standard form a + i b:

\[\left( \frac{1}{1 - 4i} - \frac{2}{1 + i} \right)\left( \frac{3 - 4i}{5 + i} \right)\]

Sum
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Solution

`(1/(1 - 4i) - 2/(1 + i))((3 - 4i)/(5 + i))`

= `(1 + i - 2(1 - 4i))/((1 - 4i)(1 + i)) xx (3 - 4i)/(5 + i)`

= `(1 + i - 2 + 8i)/(1(1 + i)-4i(1 + i))xx (3 - 4i)/(5 + i)`

= `(-1+9i)/((1 + i - 4i + 4)) xx (3 - 4i)/(5 + i)`

= `(-1 + 9i)/((1 + i - 4i + 4)) xx (3 - 4i)/(5 + i)`

= `(-1(3 - 4i) + 9i(3 - 4i))/((5 - 3i)(5 + i))`

= `(-3 + 4i + 27i + 36)/(5(5 + i)-3i(5 + i))`

= `(33 + 31j)/(25 + 5i - 15i + 3)`

= `(33 + 31j)/(28 - 10i)`

= `(33 + 31j)/(28 - 10i) xx ((28 + 10i))/(28 + 10i)`

= `(33 xx 28 + 33 xx 10i + 31i xx 28 + 31i xx 10i)/(28^2 + 10^2)`

= `(924 + 330i + 868i - 310)/(784 + 100)`

= `(614 + 1198i)/(884)`

= `614/884 + (1198)/884 i`

= `307/442 + 599/442 i`

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Chapter 13: Complex Numbers - Exercise 13.2 [Page 31]

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RD Sharma Mathematics [English] Class 11
Chapter 13 Complex Numbers
Exercise 13.2 | Q 1.11 | Page 31

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