1. ((с²-25)/(с+3))*(1/(с²+5с))=((с-5)*(с+5))*(1/(c*(c+3)*(с+5))=(с-5)/(c*(c+3)).
2. (c²+10c+25)/(c³-6c²+9c)=(c+5)²/(c*(c²-6c+9))=(c+5)²/(c*(c-3)²)
3. (c+5)²/(c*(c-3)²):((c+5)/(c-3))=(c+5)/(c*(c-3)).
4. (c-5)/(c*(c+3))-((c+5)/(c*(c-3))=((c-5)*(c-3)-(c+5)*(c+3))/((c*(c+3)*(c-3))=
=(c²-8c+15-(c²+8c+15))/(c*(c+3)*(c-3))=(c²-8c+15-c²-8c-15)/(c*(c+3)*(c-3))=
=-16c/(c*(c+3)*(c-3))=-16/((c+3)*(c-3)).
5. (4/(c-3))²=16/(c-3)².
6. -16/((c+3)*(c-3))+16/(c-3)²=(-16*(c-3)+16*(c+3))/((c+3)*(c-3)²)=
=(-16c+48+16c+48)/((c-3)*(c²-9))=96/((c-3)*(c²-9)).