Mathematics

Mathematics

Problem

8. Find the real numbers xx and yy if (x−iy)(3+5i)(x-i y)(3+5 i) is the conjugate of −6−24i-6-24 i.
Intuitive explanation

The conjugate of −6−24i-6-24i is −6+24i-6+24i, so you need to solve (x−iy)(3+5i)=−6+24i(x-iy)(3+5i) = -6+24i. The key insight is to expand the left side using FOIL, separate the real and imaginary parts, and set up a system of two equations in two unknowns. This turns a complex number equation into an algebra problem you already know how to solve.

Intuitive explanation

The conjugate of −6−24i-6-24i is −6+24i-6+24i, so you need to solve (x−iy)(3+5i)=−6+24i(x-iy)(3+5i) = -6+24i. The key insight is to expand the left side using FOIL, separate the real and imaginary parts, and set up a system of two equations in two unknowns. This turns a complex number equation into an algebra problem you already know how to solve.

Browse the problem library