1) (x+3)² = x²+6x+9
2) (2m-5)² = 2m²-20m+25
3) (7a+6b)² = 49a²+84ab+36b²
4) (x+4)²-16 = x²+8x+16-16 = x²+8x
5) 10a-(a-5)² = 10a-(a²-10a+25)=10a-a²+10a-25=-a²-25=a²+25
6) (-2a+3)² = 4a²-12a+9
7) (3m-7n)²-(3m+7n)² = 9m²-42mn+49n²-9m²-42mn-49n²=-84mn
8) b(b+3)-(b-4)² = b²+3b-(b²-8b+16)=b²+3b-b²+8b-16=11b-16