I am confused with solving for horizontal asymptotes. I know you are supposed to find limits to positive and negative infinity. I am able to solve for positive infinity but how are you supposed to do it for negative infinity, since you are not actually plugging in a particular value. This problem sounds like a silly question but it's really confusing me. An example would be (4x)/(((x^4)+1)^(1/4)) I know the limit at positive infinity is 4, but why is it -4 at negative infinity? Thanks!