A function fff is concave up if:
f′(x)>0f'(x) > 0f′(x)>0
f′′(x)>0f''(x) > 0f′′(x)>0
f′(x)<0f'(x) < 0f′(x)<0
f′′(x)<0f''(x) < 0f′′(x)<0