The correct option is D 29 Since i^2= 1 and (a+b)(a b)=a^2 b^2 ⇒ (5+2i)(5 2i) #160; =(5)^2 (2i)^2 =25 4i^2 =25 4( 1) ...

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Equations Reducible to the Linear Form

Find 5 + 2i...

Question

Find $(5 + 2 i) (5 - 2 i)$

25 - 4 i

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25 - 20 i

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21

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29

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0

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Solution

The correct option is D $29$
Since $i^{2} = - 1$ and $(a + b) (a - b) = a^{2} - b^{2}$
$\Rightarrow (5 + 2 i) (5 - 2 i)$ $= (5)^{2} - (2 i)^{2}$
$= 25 - 4 i^{2}$
$= 25 - 4 (- 1)$
$= 25 + 4$
$= 29$

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