12x-6x^2
2y-6xy^3
6x^2-3
3xy^2-6x
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Answer:
12x-6x^2 --> 6x (2-x)
2y-6xy^3 --> 2y (1-3xy^2)
6x^2-3 --> 3 (2x^2-1)
3xy^2-6x --> 3x (y^2-2)