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Ответ:

Объяснение:

а) (2m)/(3m+3) +(5m)/(6m+6)=(2m)/(3(m+1)) +(5m)/(6(m+1))=(12m+15m)/(18(m+1))=(27m)/(18(m+1))=(3m)/(2(m+1))

б) (c²+1)/(c²-2c+1) -(c+1)/(c-1)=(c²+1)/(c-1)² -((c+1)(c-1))/(c-1)²=(c²+1-c²+1)/(c-1)²=2/(c-1)²

в) (a-1)/(a+1) -(a+1)/(a-1) +4/(a²-1)=((a-1)²-(a+1)²)/((a+1)(a-1)) +4/((a-1)(a+1))=((a-1-a-1)(a-1+a+1)+4)/((a-1)(a+1))=(-2·2a+4)/((a-1)(a+1))=(-4(a-1))/((a-1)(a+1))=-4/(a+1)