25b^2 + 40b + 16 / 5b + 4

**Answer:**

**Step-by-step explanation:**

To simplify the rational expression (25b^2 + 40b + 16) / (5b + 4), we first need to factor the numerator and denominator.

The numerator can be factored as (5b + 4)(5b + 4), which simplifies to (5b + 4)^2.

The denominator is already in its simplest form as 5b + 4.

Therefore, the simplified form of the rational expression is (5b + 4)^2 / (5b + 4).