8ax²-4ax+1/2a-2ay²=1/2a(16x²-8x+1-4y²)=1/2a[(16x²-8x+1)-4y²]=1/2a[(4x-1)²-4y²]=1/2a[(4x-1)-2y][(4x-1)+2y]=1/2a(4x-1-2y)(4x-1+2y)