To simplify the expression b² + 10b + 25 / 8b + 25, we need to factor the numerator and denominator if possible.

Factoring the numerator:
b² + 10b + 25 = (b + 5)(b + 5) = (b + 5)²

Factoring the denominator:
8b + 25 = 8b + 25 = 8(b + 25/8)

Now the expression becomes:
(b + 5)² / 8(b + 25/8)

Now we can simplify further if needed.