We'll assume the quadratic equation has real coefficients
Answer:
The other solution is x=1-8i.
Step-by-step explanation:
The Complex Conjugate Root Theorem
if P(x) is a polynomial in x with real coefficients, and a + bi is a root of P(x) with a and b real numbers, then its complex conjugate a − bi is also a root of P(x).
The question does not specify if the quadratic equation has real coefficients, but we will assume that.
Given x=1+8i is one solution of the equation, the complex conjugate root theorem guarantees that the other solution must be x=1-8i.
