\(1)\left(2x+1\right)^2+\left(2x-1\right)^2\\ =4x^2+4x+1+4x^2-4x+1\\ =8x^2+2\\ 2)-\left(x+1\right)^2-\left(x-1\right)^2\\ =-\left(x^2+2x+1\right)-\left(x^2-2x+1\right)\\ =-x^2-2x-1-x^2+2x-1\\ =-2x^2-2\\ 3)\left(x+2y\right)^2-\left(x-2y\right)^2\\ =x^2+4xy+4y^2-x^2+4xy-4y^2\\ =8xy\)
1: \(\left(2x+1\right)^2+\left(2x-1\right)^2\)
\(=4x^2+4x+1+4x^2-4x+1\)
\(=8x^2+2\)
2: \(-\left(x+1\right)^2-\left(x-1\right)^2\)
\(=-x^2-2x-1-x^2+2x-1\)
\(=-2x^2-2\)
3: \(\left(x+2y\right)^2-\left(x-2y\right)^2\)
\(=\left(x+2y+x-2y\right)\left(x+2y-x+2y\right)\)
\(=2x\cdot4y=8xy\)
