The function m(x), as x approaches positive or negative infinity, depends mostly on the therm x³/3.
Since x³/3 is positive for positive values of x, and grows when x grows, m(x) approaches positive infinity as x approaches positive infinity.
On the other hand, x³/3 is negative for negative values of x, and decreases when x decreases. So, as x approaches negative infinity, m(x) approaches negative infinity, as we can see in the graph of m(x):
Therefore:
As x approaches positive infinity, m(x) approaches positive infinity
As x approaches negative infinity, m(x) approaches negative infinity.
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