Simplify. (x3 + 2x − 3)(x4 − 3x2 + x)
 (please provide a step-by-step explanation and answer. I don't just need the answer I need to understand how to do this)
 x12 − 3x6 − x4 + x3 + 3x2 − x
 x12 − 3x6 − x4 + x3 − 15x2 − x
 x7 − x5 − 2x4 − 6x3 + 11x2 − 3x
 x7 − 5x5 − 2x4 − 6x3 + 11x2 − 3x