4xy^2-2x^2y-y^3
=-y(2x²-4xy+y²)
=-y(2x²-4xy+2y²-y²)
=-y[2(x²-2xy+y²)-y²]
=-y[2(x-y)²-y²]
=-y[√2(x-y)+y][√2(x-y)-y]
=-y(√2x-√2 y+y)(√2x-√2 y-y)
(4a^2+1)^2-16a^2
=(4a²+1+4a)(4a²+1-4a)
=(2a+1)²(2a-1)²
4xy^2-2x^2y-y^3
=-y(2x²-4xy+y²)
=-y(2x²-4xy+2y²-y²)
=-y[2(x²-2xy+y²)-y²]
=-y[2(x-y)²-y²]
=-y[√2(x-y)+y][√2(x-y)-y]
=-y(√2x-√2 y+y)(√2x-√2 y-y)
(4a^2+1)^2-16a^2
=(4a²+1+4a)(4a²+1-4a)
=(2a+1)²(2a-1)²