Concavity Example Where is the function f ( ac ) = - 23 - 3x2 + 8x concave up and where is it concave down? Solution: We have f"(x) = 2x - 6. Put f"(x) = 0 and x = 3. Choose x = 0 as the test number in (-oo, 3) and x - 5 as the test number in (3, 00). Since f"(0) = -6 0, f is concave upward when x > 3. (MATH2005 / MATH2006) Applications of Differentiation Second Semester 2021 27 /45