1) (a+7)^2+(a-2)(a+5)-7a= a^2+14a+49+a^2+5a-2a-10-7a=2a^2+10a+39
2) (a-6)^2+(a+3)(a-5)+7=a^2-12a+36+a^2-5a+3a-15+7
3) -(a-3)^2+(a+6)(a-2)-8a=-(a^2+6a-9)+a^2-2a+6a-12-8a=-a^2+6a-9+a62-2a+6a-12-8a
4) 8-(a+5)^2-(a-4)(a+7)+16a=8-(a^2+10a+25)-(a^2+7a-4a-28)+16a=8-a^2-10a-25-(a^2+3a-28)+16a=8-a^2-10a-25-a^2-3a+28+16a=11-2a^2+3a=-2a^2+3a+11