Perform a calculation: 3xn(4xn-1 - 1) - 2xn+1(6xn-2 - 1)
\(3x^n.\left(4x^{n-1}-1\right)-2x^{n+1}\left(6x^{n-2}-1\right)\\ =12x^{n+n-1}-3x^n-12x^{n+1+n-2}+2x^{n+1}\\ =2x^{n+1}-3x^n\)
