Factorise x3 - 23x2 + 142x - 120

x³ - 23x² +142x -120

Note that putting x=1 the value of the expression becomes zero.

Thus by the factor theorem (x-1) is a factor of the given polynomial.

The polynomial is a 3 degree polynomial and hence has 3 factors.

To get the other 2 factors divide the given polynomial by (x-1) and factorize the 2 degree polynomial obtained by middle term splitting.