Let a + b i and c + d i denote two nonzero, complex numbers such that
True or False?
There exists at least one solution ( a , b , c , d ) that satisfies the following equation: c + d i a + b i = c a + d b i .
Note: i = − 1 is the imaginary unit .
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Let's rationalize the first quotient of complex numbers according to:
c + d i a + b i ⋅ c − d i c − d i = c 2 + d 2 ( a + b i ) ( c − d i ) = c 2 + d 2 a c + b d + c 2 + d 2 b c − a d i (i).
We now require matching the real and the imaginary parts above:
c 2 + d 2 a c + b d = c a & c 2 + d 2 b c − a d = d b ;
or b c = a d (REAL) & b c d − a d 2 = b c 2 + b d 2 (IMAGINARY) (ii). Substituting the real expression into the imaginary side simplifies the latter into:
b c d − a d 2 = b c 2 + b d 2 ⇒ ( a d ) d − a d 2 = ( a d ) c + b d 2 ⇒ a d 2 − a d 2 = d ( a c + b d ) ⇒ 0 = d ( a c + b d ) (iii)
Since d = 0 , we require a c + b d = 0 ⇒ d = − b a c (iv). A final substitution back into the real expression of (ii) now yields:
b c = a d ⇒ b c = a ( − b a c ) ⇒ b 2 c = − a 2 c ⇒ a 2 + b 2 = 0 ⇒ a = b = 0
which makes the original complex number a + b i = 0 (CONTRADICTION).
That can easily be done with z = r e θ i , but your way is fine and good! :)
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Assume there exists at least a solution of ( a , b , c , d ) that satisfies the following equation
c + d i a + b i ⟹ a + b i Equating a ⟹ b Equating b 0 since d = 0 ⟹ ( a + b i ) Since a + b i Thus there = c a + d b i = ( c + d i ) × ( c a + d b i ) = ( a − b ) + ( d b c + c a d ) i real parts we get, = ( a − b ) = 0 ( 1 ) imaginary parts we get, = ( d b c + c a d ) = c a d from ( 1 ) we must have a = 0 = 0 + 0 i is a nonzero complex number, our assumption that a solution exists is wrong. exists no solution for the given equation.