`b)`

`a^2-x^2+4ab+4xy+b^2-4y^2`

`=(a^2+4ab+b^2)-(x^2-4xy+4y^2)`

`=(a+b)^2-(x-2y)^2`

`=(a+b-x+2y)(a+b+x-2y)`

`c)`

`x^3+y^3+3x^2-3xy+3y^2`

`=(x+y)(x^2-xy+y^2)+3(x^2-xy+y^2)`

`=(x^2-xy+y^2)(x+y+3)`

`3B`

`a)`

`9x^2-6xy+y^2-a^2+4ab-4b^2`

`=(9x^2-6xy+y^2)-(a^2-4ab+4b^2)`

`=(3x-y)^2-(a-2b)^2`

`=(3x-y-a+2b)(3x+a-2b)`

`b)`

`a^2+b^2-4x^2-y^2-2ab+4xy`

`=(a^2-2ab+b^2)-(4x^2-4xy+y^2)`

`=(a-b)^2-(2x-y)^2`

`=(a-b-2x+y)(a-b+2x-y)`

`c)`

`x^3-3x^2y+x+3xy^2-y-y^3`

`=(x^3-3x^2y+3xy^2-y^3)+(x-y)`

`=(x-y)^3+(x-y)`

`=(x-y)[(x-y)^2+1]`

`=(x-y)(x^2-2xy+y^2+1)`