\(\left(2xy+1\right)^2-\left(2xy+y\right)^2\)
= \(\left[\left(2xy+1\right)-\left(2xy+y\right)\right]\left[\left(2xy+1\right)+\left(2xy-1\right)\right]\)
= \(\left[2xy+1-2xy+y\right]\left[2xy+1+2xy-1\right]\)
= \(\left[\left(2xy-2xy\right)+\left(1+y\right)\right]\left[\left(2xy+2xy\right)+\left(1-1\right)\right]\)
= \(y.4xy\)