Answer:
 Quantity B is greater.
Explanation:
Given:
 (x -2y)(x +2y) = 4
 A = x² -4y²
 B = 8
Find:
 the relationship between A and B
Solution:
The given expression can be expanded to give ...
 x(x +2y) -2y(x +2y) = x² +2xy -2xy -4y² = x² -4y²
This is precisely the expression designated as A. Its value is 4.
 4 < 8
 A < B
Quantity B is greater.