It looks like you have already done so correctly, except for omitting some important parentheses..
5(y-1)/[(y-1)(y-4)] = 5/(y-4)
expression in lowest terms
5(y-1)/(y-1)(y-4)
=5/y-4
1 answer
5(y-1)/(y-1)(y-4)
=5/y-4
1 answer