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Mathematics
Mathematics
Problem
Let
f
(
x
)
f(x)
f
(
x
)
be continuous and differentiable function for all reals and
f
(
x
+
y
)
=
f
(
x
)
−
3
x
y
+
f
(
y
)
f(x+y) = f(x) - 3xy + f(y)
f
(
x
+
y
)
=
f
(
x
)
−
3
x
y
+
f
(
y
)
. If
lim
h
→
0
f
(
h
)
h
=
7
\lim_{h \to 0} \frac{f(h)}{h} = 7
lim
h
→
0
h
f
(
h
)
=
7
, then the value of
f
′
(
x
)
f'(x)
f
′
(
x
)
is a.
−
3
x
-3x
−
3
x
b. 7 c.
−
3
x
+
7
-3x + 7
−
3
x
+
7
d.
2
f
(
x
)
+
7
2f(x) + 7
2
f
(
x
)
+
7
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