Add.

To add the expressions \( (-4n - 1) + (-9n + 7) \), you can follow these steps:

1. Combine like terms:

   • Combine the \( n \)-terms: \( -4n + (-9n) = -4n - 9n = -13n \)
   • Combine the constant terms: \( -1 + 7 = 6 \)

2. Write the combined expression: \[ -13n + 6 \]

So, the sum of the expressions is: \[ -13n + 6 \]