3.

1) (a²-4)/(7a+14)=(a+2)(a-2)/7(a+2)=(a-2)/7

2) (y²-49)/y²+5y-14=(y+7)(y-7)/(y²-2y +7y-14) =(y+7)(y-7)/(y(y-2+7(y-2))=(y+7)(y-7)/(y-2)(y+7)=(y-7)/(y-2)