1.Use a sign chart to determine the open intervals on which is increasing and the open intervals on which is decreasing.Then determine the critical numbers and the local extrema for each function. Hint : First derivative test.

f(x)=x⁴-18x²

2.Use a sign chart to find the open intervals on which the graph of is concave upward, the open intervals on which the graph of is concave downward, and the inflection points.

Hint : Second derivative testf(x)=-0.25x⁴+x³