The negative sign in front of the parentheses changes the signs of the items inside the parentheses. The 2q becomes -2q and the +1 becomes -1. That means that the negative sign in front of the parentheses tells you to take the "opposite" of everything inside the parentheses.
Your statement should now read 9q-4-2q-1. Combining like terms means that 9q-2q becomes 7q and -4-1 becomes -5. Your answer should be 7q-5.
9q-4-(2q+1), first you need to open the brackets, by multiplying the values by the negative sign before the brackets to get 9q-4-2q-1. Then, collect the like terms together, 9q ? 2q ? 4 - 1. The answer will be 7q-5.