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Mathematics
Mathematics
Problem
If the graph of a twice-differentiable function
f
f
f
is concave down on the open interval
(
1
,
6
)
(1,6)
(
1
,
6
)
, which of the following statements must be true for every
x
x
x
in
(
1
,
6
)
(1,6)
(
1
,
6
)
? a)
f
′
(
x
)
<
0
f'(x)<0
f
′
(
x
)
<
0
b)
f
′
′
(
x
)
<
0
f''(x)<0
f
′′
(
x
)
<
0
c)
f
′
′
(
x
)
=
0
f''(x)=0
f
′′
(
x
)
=
0
d)
f
′
′
(
x
)
>
0
f''(x)>0
f
′′
(
x
)
>
0
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