(a-1)分之(2a+2)÷(a+1)+(a²-2a+1)分之(a²-1)
=(a-1)分之2(a+1)÷(a+1)+(a-1)²分之(a+1)(a-1)
=(a-1)分之2+(a-1)分之(a+1)
=(a-1)分之(a+3)