12C6{ }^{12} \mathrm{C}_{6}12C6
12C5x2{ }^{12} \mathrm{C}_{5} \mathrm{x}^{2}12C5x2
−12C5x4-{ }^{12} \mathrm{C}_{5} x^{4}−12C5x4
−12C5x-{ }^{12} \mathrm{C}_{5} \mathrm{x}−12C5x