Final answer:
The difference of the two squares in the expression (7x+7y)(7x-7y) is 49x² - 49y².
Step-by-step explanation:
To find the difference of the two squares in the expression (7x+7y)(7x-7y), we can apply the formula a^2 - b^2, where a represents the first term and b represents the second term. In this case, a = 7x and b = 7y.
Substituting these values into the formula, we get (7x)^2 - (7y)^2 = 49x^2 - 49y^2. Therefore, the difference of the two squares is 49x^2 - 49y^2.
So, the correct option is a) 49x² - 49y².