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limx→3(1/x-3–27/x的3次方-27)怎么做
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limx→3(1/x-3 – 27/x的3次方-27)怎么做
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答案和解析
1/(x-3)-27/(x³-27)=【(x²+3x+9)-27】/(x³-27)=(x²+3x-18)/(x³-27)=(x+6)(x-3)/(x-3)(x²+3x+9)=(x+6)/(x²+3x+9)所以当x→3时,lim【1/(x-3)-27/(x...
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