Question

25x^2 - 10xy+y^2- 9 ​

Answer 1

$25 {x}^{2} - 10xy + {y}^{2} - 9 = (5x - y)^{2} - 9$

Answer 2

Разложение на множители:

$25x^2-10xy+y^2-9=(5x-y)^2-3^2=\\=(5x-y-3)(5x-y+3)$