Factorise `a^3-b^3+1+3ab`.

1.	Factorise `a^3-b^3+1+3ab`.
Answer» We have `a^3-b^3+1+3ab` `=a^3+(-b)^3+(1)^3-3xx a xx (-b)xx 1` `=x^3+y^3+z^3-3xyz, " where" a =x, (-b) =y and 1=z` `=(x+y+z)(x^2+y^2+z^2-xy-yz-zx)` `=(a-b+1)(a^2+b^2+1+ab+b-a)` `=(a-b+1)(a^2+b^2+ab-a+b1)`.

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