1). a(a-2b)-(3b+a)=a²-2ab-3b-a
2). (m+8)^2-(m-2n)(m+2n)=m²+16m+64-m²+4n² = 4n²+16m+64
3). 3(b-10)^2+8b-5b^2=3b²-60b+300+8b-5b² = 300 - 52b -2b²
4). (n+15)^2-n(n-19)=n²+30b+225-n²+19n = 49n+225
5). 4c(9c-3)-(6c+1)^2=36c²-12c-36c²-12c-1 = -24c - 1
6). (6-5m)(5m+6)+(5m-4)^2= 36-25m² + 25m²-40m+16 = 52 - 40m