Hi guys,

I'm doing limit exercises and I got this question:

Evaluate the following limit:

lim

x → −∞ √(x2 + 5 x + 1) - x

After working it out by multiplying by conjugate I get 5/0 which is undefined, but I know the answer is infinity. So where did I go wrong? This is the last step which I deduced 5/0 from:

(5 + (0))/-sqrt(1 + (0) + (0)) + 1

Any clarification is appreciated