The end behavior of a function behaves as if only the highest order variable existed.
In this case only the behavior of 4x^5 determines the end behavior of the function.
The left-hand behavior, as x approaches negative infinity, is for the function to decrease without bound as a negative raised to an odd power is negative.
The right-hand behavior, as x approaches positive infinity, is for the function to increase without bound as a positive raised to a positive value is positive.