For distinct positive integers , how many complex numbers satisfy the equation
Note: is the complex conjugate of
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We first note that z = 0 is a solution for all positive p , q .
Next, every non-zero complex number can be written uniquely as z = r ⋅ e i θ where r > 0 , 0 ≤ θ < 2 π . We note that this implies that ∣ ∣ z a ∣ ∣ = r a when written in this form since ∣ ∣ e i x ∣ ∣ = 1 , ∀ x . Also, note that z ˉ = r ⋅ e − i θ .
Thus, if the given equation is correct, then we first have
∣ ∣ z p ∣ ∣ = ∣ ∣ z ˉ q ∣ ∣ ⇒ r p = r q .
For positive real r , this only has solutions at r = 1 . Thus our original problem is reduced to
e i θ p = e − i θ q ⇒ e i θ ( p + q ) = 1 .
From here, we see that we must have
θ ⋅ ( p + q ) = 2 π n
for natural n , and restricting to the interval 0 ≤ θ < 2 π we have our entire set of solutions:
z = 0 , e 2 π i / ( p + q ) , e 2 ⋅ 2 π i / ( p + q ) , … , e ( p + q − 1 ) ⋅ 2 π i / ( p + q )