Mathematics

Problem

Which of the following statements best describes when the graph of a differentiable function

f

is concave up on an open interval

I

? a)

f'(x)>0

for every

x \text{ in } I

. b)

f''(x)<0

for every

x \text{ in } I

. c)

f''(x)>0

for every

x \text{ in } I

. d)

f'(x)

is decreasing on

I