a/ \(=\left(4x^2+4x+1\right)-4y^2=\left(2x+1\right)^2-\left(2y\right)^2\)
\(=\left(2x-2y+1\right)\left(2x+2y+1\right)\)
b/
\(=9x^2-9y^2+6y-1=\left(3x\right)^2-\left(9y^2-6y+1\right)\)
\(=\left(3x\right)^2-\left(3y-1\right)^2=\left(3x-3y+1\right)\left(3x+3y-1\right)\)
c/
\(=\left(8x+12\right)^2-\left(15x-6\right)^2\)
\(=\left(8x+12-15x+6\right)\left(8x+12+15x-6\right)\)
\(=\left(-7x+18\right)\left(23x+6\right)\)