Explanation:

Let’s break it down:

- You're looking for the value of $(2a+b)^2 - (2a-b)^2$.

- First, we expand both terms:

- $(2a+b)^2 = (2a)^2 + 2 \cdot 2a \cdot b + b^2 = 4a^2 + 4ab + b^2$

- $(2a-b)^2 = (2a)^2 - 2 \cdot 2a \cdot b + b^2 = 4a^2 - 4ab + b^2$

- Now, subtract the second from the first:

- $[4a^2 + 4ab + b^2] - [4a^2 - 4ab + b^2]$

- $4a^2 - 4a^2 + 4ab - (-4ab) + b^2 - b^2$

- $0 + 8ab + 0 = 8ab$

Now let’s quickly scan through the options:

1. 8ab  

2. 7ab (not correct—the math above shows 8, not 7)

3. 8a² + 2b (not matching the derived expression)

4. 8a² - 2b² (again, different variables and no $ab$ term)

What this really means is: whenever you see an expression like $(x+y)^2 - (x-y)^2$, you’re looking at $4xy$. Just remember that nuance, and you'll be set for questions like this every time.