SOLUTION
Concavity interval definitions is given as
If f"(x) > 0, then f(x) concave upwards
If f"(x) < 0, then f(x) concave downwards
[tex]f^{\prime}^{\prime}(x)=2x-6[/tex]equating to zero, we have
[tex]concave\text{ }downward:-\inftyso, cocave downwards becomes [tex]-\infty
