1 \(=\left(4x^2+4x+1\right)-\left(3y\right)^2\)
\(=\left(2x+1\right)^2-\left(3y\right)^2\)
\(=\left(2x+1-3y\right)\left(2x+1+3y\right)\)
2,\(=\left(x^2+2xy+y^2\right)-\left(z^2-2zt+t^2\right)\)
\(=\left(x+y\right)^2-\left(z-t\right)^2\)
\(=\left(x+y+z-t\right)\left(x+y-z+t\right)\)
3,\(=9x\left(x-y\right)-7\left(x-y\right)\)
\(=\left(x-y\right)\left(9x-7\right)\)
4\(=3\left(x-y\right)+a\left(x-y\right)\)
\(=\left(x-y\right)\left(3+a\right)\)