Answer :

Let's find the sum of the given expressions step-by-step:

Given expressions:
[tex]\[ (2n^2 - 5n - 6) + (-n^2 - 3n + 11) \][/tex]

1. Combine like terms:

a) Combine the [tex]\(n^2\)[/tex] terms:
[tex]\[ 2n^2 + (-n^2) = 2n^2 - n^2 = n^2 \][/tex]

b) Combine the [tex]\(n\)[/tex] terms:
[tex]\[ -5n + (-3n) = -5n - 3n = -8n \][/tex]

c) Combine the constant terms:
[tex]\[ -6 + 11 = 5 \][/tex]

2. Sum up the results:

Combine all the simplified terms to get the final expression:
[tex]\[ n^2 - 8n + 5 \][/tex]

So, the sum of the given expressions is:
[tex]\[ \boxed{n^2 - 8n + 5} \][/tex]