x-1 1 2
1 x-5 0
2 0 x-5
r3-2r2
x-1 1 2
1 x-5 0
0 -2(x-5) x-5
c2+2c3
x-1 5 2
1 x-5 0
0 0 x-5
= (x-5)[(x-1)(x-5)-5]
= (x-5)(x^2-6x)
= x(x-5)(x-6).