Объяснение:
1) 2а-1/5b + a/b= 2a-1+5a/5b= 7a-1/5b
2) 3/x²-1 - 2/x-1 = 3/(x-1)(x+1) - 2/x-1= 3-2x-2/(x-1)(x+1)= 1-2x/(x-1)(x+1)
