Problem
NT-B1-M12-P016 Set 3. Difference of Squares
#16
★★★☆☆ Level 3 of 5
Find all positive integers \(x>y\) such that \(x^2-y^2=840\).
Set \(x-y=2u\), \(x+y=2v\).
Since \(x-y\) and \(x+y\) have the same parity and their product is \(840\), both factors are even. Let \(x-y=2u\), \(x+y=2v\). Then \(uv=210\), \(u
Long but fully controlled factorisation.