Answer:
[tex](2x - 5)^2[/tex]
Step-by-step explanation:
[tex]y = 4x^2 -20x + 25\\\rightarrow (2x - 5)(2x - 5)\\\rightarrow (2x - 5)^2\\\\\text{checking...}\\(2x - 5)^2 = (2x - 5)(2x - 5) = 4x^2 - 10x - 10x + 25 = 4x^2 - 20x + 25[/tex]