In (c) just find the roots of the quadratic equation you're trying to factor, which are 4 and . So one factor would have to be and the other would have to be . Try something similar to the other problem you're working on.
The minus comes from the 3- 4y in the original problem. In order to be able to cancel with the 4y- 3 which is a factor , Soroban factored out a "-1" writing it as -(4y- 3).