I have problems with the directions: Find the limit of each rational function as...

a) x approaches infinity

b) x approaches - infinity

Can someone show me how I would do a problem such as

f(x) = (2x + 3) / (5x +7)

and

h(x) = 7x^3 / (x^3 - 3x^2+6x)

Thanks so much I have a bunch of these to do, so seeing/understanding these would really help!