2a^2b+4ab-2b
=2b(a^2+2a-1)
=2b(a+1+√2)(a+1-√2)
16x^4-8x^2y^2+y^4
=(4x^2)^2-2×4x^2×y^2+(y^2)^2
=(4x^2-y^2)^2
=(2x+y)^2(2x-y)^2