
对于函数f(x),已知f(3)=2,f′(3)=-2,求limx→32x?3f(x)x?3
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∵f(3)=2,f′(3)=-2,
∴
=
=
+
=
2?3
=2-3f′(3)
=2-3×(-2)
=8.
∴
lim |
x→3 |
2x?3f(x) |
x?3 |
=
lim |
x→3 |
2x?3f(3)+3f(3)?3f(x) |
x?3 |
=
lim |
x→3 |
2x?3×2 |
x?3 |
lim |
x→3 |
?3(f(x)?f(3)) |
x?3 |
=
lim |
x→3 |
lim |
x→3 |
f(x)?f(3) |
x?3 |
=2-3f′(3)
=2-3×(-2)
=8.
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