則
lim |
h→0 |
f(x0+h)-f(x0-h) |
h |
=
lim |
h→0 |
f(x0+h)-f(x0)+f(x0)-f(x0-h) |
h |
=
lim |
h→0 |
f(x0+h)-f(x0) |
h |
lim |
-h→0 |
f(x0-h)-f(x0) |
-h |
=2f′(x0)=-6.
故選;B.
lim |
h→0 |
f(x0+h)-f(x0-h) |
h |
lim |
h→0 |
f(x0+h)-f(x0-h) |
h |
lim |
h→0 |
f(x0+h)-f(x0)+f(x0)-f(x0-h) |
h |
lim |
h→0 |
f(x0+h)-f(x0) |
h |
lim |
-h→0 |
f(x0-h)-f(x0) |
-h |