The lead term determines the end behavior....we only have 4 rules to remember
1) Sign on lead coefficient positive and even exponent on the variable on the lead term
As x → pos/neg infinity , f (x) → pos infinity
2) Sign on lead coefficient positive and odd exponent on the variable on the lead term
As x → neg infinity, f(x) → neg infinity
As x → pos infinity, f(x) → pos infinity
[ Note that this one would apply to the first polynomial]
3) Sign on lead coefficient negative and an even exponent on the variable on the lead term
As x → neg infinity, f(x) → neg infinity
As x → pos infinity, f(x) → neg infinity
[ This applies to the second polynomial ]
4) Sign on lead coefficient negative and an odd exponent on the variable on the lead term
As x → pos/neg infinity, f(x) → neg infinity