1/(x2-x)+4/(x2-3x-4)=(x2-3x-4+4x2-4x)/[(x2-x)(x2-3x-4)]=
(5x2-7x-4)/[(x2-x)(x2-3x-4)].
I think x2-3x-4 should have been x2+3x-4, in which case the expression simplifies:
1/(x2-x)+4/(x2+3x-4)=
1/[x(x-1)]+4/[(x-1)(x+4)]=(x+4+4x)/[x(x-1)(x+4)]= (note that the LCD is x(x-1)(x+4))
(5x+4)/(x3+3x2-4x).
Alternatively, x2-x should have been x2+x:
1/[x(x+1)]+4/[(x+1)(x-4)]=(x-4+4x)/[x(x+1)(x-4)]=
(5x-4)/(x3-3x2-4x).