# Number theory-product of squares

by diracy
Tags: number, squares, theoryproduct
 P: 20 1. The problem statement, all variables and given/known data Suppose a and b are two integers, which can each be written as the sum of two squares. Prove that ab can be expressed as the sum of two squares. 2. Relevant equations 3. The attempt at a solution a=c$^{2}$+d$^{2}$ b=x$^{2}$+y$^{2}$ I'm not exactly sure how to approach this proof.