Since we have that the polynomial 2x - 1 is a factor, it signifies that, if we divide the dividend (the original polynomial) by this factor, we will have another factor of the polynomial, and this other polynomial can be obtained using the long division:
As we can see, doing the long division operation, we have that the other factor is:
And, from the options, we have that is the first option that is correct.
In summary, the expression that represents the other factor is x²+3x-12 (first option).