Help!!

Not sure about the  first one  .....but....for the second one

We have a  same degree polynomial . same degree polynomial   situation....so.....the  limit  of  nth term as x  becomes increasingly large  is just the ratio  of the coefficients on the highest power terms in the numerator and  denominator....so  we  have

8 / 6    =  

4 / 3

For the first one, note that the term 3n⁵/(4n⁵ + 1)  gets very close to 3/4 by the time n has reached 10 or so.  What that means is that the sum consists of an infinite number of values that are all very nearly 3/4.  Adding an infinite number of 3/4 results in an infinite sum.