Let's simplify the given expression:
(5x+1)(5x-1) - (5x+1)² = (25x² - 5x + 5x - 1) - (25x² + 10x + 1) = (25x² - 1) - (25x² + 10x + 1) = 25x² - 1 - 25x² - 10x - 1 = -10x - 2
Therefore, the expression (5x+1)(5x-1) - (5x+1)² simplifies to -10x - 2.
Let's simplify the given expression:
(5x+1)(5x-1) - (5x+1)²
= (25x² - 5x + 5x - 1) - (25x² + 10x + 1)
= (25x² - 1) - (25x² + 10x + 1)
= 25x² - 1 - 25x² - 10x - 1
= -10x - 2
Therefore, the expression (5x+1)(5x-1) - (5x+1)² simplifies to -10x - 2.