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How to find the square root …

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How to find the square root of -7-24i ?

  • 1 answers

Naveen Sharma 7 years, 1 month ago

Ans. 

Let {tex}\sqrt {-7-24i} = x+yi{/tex}

Squaring Both Sides,

=> -7-24i = x2 - y+ 2xyi

on comparing, we get

=> x2 - y= -7   ……(1)

and 2xy = -24 ………(2)

We know

(x2+y2)= (x2-y2)2 + 4x2y2

=> (x2+y2)2 = 49 + 576

=> (x2+y2)= 625

=> x2+ y2 = 25  …………(3)

solving (2) and (3), We get

{tex}x = \pm 3 \space \space \space and \space y =\pm4{/tex}

from (2) as product of xy is -ve, so it means x and y are of opposite sign.

So, when x = 3, y = -4

when x = -3, y = 4

Therefore, 

{tex}\sqrt {-7-24i} = \pm (3-4i){/tex}

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