Answer:
4ab
Step-by-step explanation:
(a+b)^2-(a-b)^2
=a^2 + 2ab + b^2 -(a^2 - 2ab +b^2)
=a^2 + 2ab + b^2 - a^2 + 2ab - b^2
=2ab + 2ab
=4ab
