1) n^2+10n+25-n^2+7n=17n+25. 2) 16c^2-6c-(16c^2+8c+1)=16c^2-6c-16c^-8c-1=-14c-1. 3)(6-n)(6+n) +(n-4)^2=36-n^2+n^2-8n+16=-8n+52