Which of the following best describes the end behavior of y=x^2 -bx +c as x approaches either positive or negative infinity? a.) y approaches positive infinity b.) y approaches positive infinity c.) y approaches c d.) y approaches -c/b

As x approaches either positive or negative infinity, y will approach positive infinity. 
This is because x^2 will grow large much quicker than b*x, so it has more importance. So when considering the limit, we can imagine that the equation looks like this:
y = x^2 
This equation will go to infinity for x approaching both negative and positive infinity.