Determine the number of solutions of the equation, where is a complex number.
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Let z = a + b i be any complex number. The above equation yields:
( a + b i ) 2 + a 2 + b 2 = 0 ;
or a 2 − b 2 + 2 a b i + a 2 + b 2 = 0
which requires both the real and the imaginary parts to equal zero:
a 2 − b 2 + a 2 + b 2 = 0 ; 2 a b = 0 .
The imaginary part is zero iff a or b = 0 . Hence for the real part:
If a = 0 , then we have − b 2 + ∣ b ∣ = 0 ⇒ b = ± b 2 . Taking b = b 2 yields b = 0 , 1 and b = − b 2 yields b = 0 , − 1 , which in turn produce the ordered-pairs ( a , b ) = ( 0 , 0 ) ; ( 0 , − 1 ) ; ( 0 , 1 ) .
If b = 0 , then we have ∣ a ∣ = − a 2 ⇒ a = 0 and ( a , b ) = ( 0 , 0 ) is the only ordered-pair solution under this condition.
Thus, ( a , b ) = ( 0 , 0 ) ; ( 0 , − 1 ) ; ( 0 , 1 ) (or z = 0 , ± i ) are the only solutions