Chapter 1 - Introduction to Algebraic Expressions - Review Exercises: Chapter 1 - Page 77: 65

$17n^2+m^2+20mn$

The given expression, $ 2n^2-5(-3n^2+m^2-4mn)+6m^2 $, simplifies to \begin{array}{l} 2n^2-5(-3n^2)-5(m^2)-5(-4mn)+6m^2 \\\\= 2n^2+15n^2-5m^2+20mn+6m^2 \\\\= (2n^2+15n^2)+(-5m^2+6m^2)+20mn \\\\= 17n^2+m^2+20mn .\end{array}