判断题若函数f（x）在点x0处无定义，则函数f（x）在点x0处极限不存在（） 如果函数在某点处无定义 则极限存在么
\u82e5\u51fd\u6570f\uff08x\uff09\u5728\uff58\u5904\u6781\u9650\u4e0d\u5b58\u5728\uff0c\u5219\u51fd\u6570\u5728\u8be5\u70b9\u65e0\u5b9a\u4e49\u3002 \u662f\u9519\u7684\uff0c\u8fd9\u91cc\u8ddf\u5de6\u53f3\u6781\u9650\u7684\u6982\u5ff5\u6ca1\u5173\u7cfb\u3002\u8001\u5e08\u53ea\u662f\u5728\u8868\u660e\u4e00\u4e2a\u8bba\u70b9\uff1a\u51fd\u6570\u5728\u67d0\u5904\u65e0\u5b9a\u4e49\u5e76\u4e0d\u8868\u793a\u51fd\u6570\u5728\u8be5\u5904\u4e00\u5b9a\u65e0\u6781\u9650\u6216\u6781\u9650\u4e0d\u5b58\u5728\uff1b\u4f46\u53cd\u8fc7\u6765\uff0c\u5982\u679c\u51fd\u6570\u5728\u67d0\u5904\u6709\u5b9a\u4e49\u4e5f\u4e0d\u8868\u793a\u51fd\u6570\u5728\u8be5\u5904\u4e00\u5b9a\u6709\u6781\u9650\u6216\u6781\u9650\u5b58\u5728\u3002\u4e5f\u5c31\u662f\u8bf4\uff0c\u51fd\u6570\u6709\u6ca1\u6709\u6781\u9650\u6216\u6781\u9650\u5b58\u4e0d\u5b58\u5728\uff0c\u4e0e\u51fd\u6570\u6709\u65e0\u5b9a\u4e49\u65e0\u5173\u3002\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u5982\u679c\u51fd\u6570\u5728\u67d0\u5904\u5b58\u5728\u5de6\u6781\u9650\uff0c\u4e14\u5b58\u5728\u53f3\u6781\u9650\uff0c\u4f46\u5de6\u3001\u53f3\u6781\u9650\u4e0d\u76f8\u7b49\uff0c\u90a3\u4e48\u51fd\u6570\u5728\u8be5\u5904\u65e0\u6781\u9650\u6216\u6781\u9650\u4e0d\u5b58\u5728\uff08\u672c\u9898\u4e0d\u6d89\u53ca\uff09\u3002
\u795d\u5b66\u4e60\u8fdb\u6b65\uff01
\u901a\u5e38\u90fd\u662f\u7531\u653e\u7f29\u6cd5\u51fa\u53d1\uff0c\u5e76\u901a\u8fc7\u6781\u9650\u5b58\u5728\u7684\u5b9a\u4e49\u5f97\u5230\u8bc1\u660e\u7ed3\u679c\u3002
\u6bd4\u5982\u4e00\u4e2a\u7b80\u5355\u7684\u4f8b\u5b50\uff1az=(xy)^2/(x^2 y^2)
\u8981\u8bc1\u660e\u5f53x,y->0\u662f\u6781\u9650\u5b58\u5728\u662f\u7531
|(xy)^2/(x^2 y^2)-0|<=|(xy)^2/(2xy)|=0.5|xy|=0\uff0c\u4ece\u800c\u6781\u9650\u5b58\u5728\u3002
\u6269\u5c55\u8d44\u6599
\u5224\u65ad\u51fd\u6570\u6709\u6ca1\u6709\u5b9a\u4e49\u7684\u65b9\u6cd5\uff1a
\u9996\u5148\u5224\u65ad\u51fd\u6570\u5728\u8fd9\u4e2a\u70b9x0\u662f\u5426\u6709\u5b9a\u4e49\uff0c\u5373f(x0)\u662f\u5426\u5b58\u5728\uff1b\u5176\u6b21\u5224\u65adf(x0)\u662f\u5426\u8fde\u7eed\uff0c\u5373f(x0-),f(x0+),f(x0)\u4e09\u8005\u662f\u5426\u76f8\u7b49\u3002
\u518d\u6b21\u5224\u65ad\u51fd\u6570\u5728x0\u7684\u5de6\u53f3\u5bfc\u6570\u662f\u5426\u5b58\u5728\u4e14\u76f8\u7b49\uff0c\u5373f\u2018(x0-)=f'(x0+)\uff0c\u53ea\u6709\u4ee5\u4e0a\u90fd\u6ee1\u8db3\u4e86\uff0c\u5219\u51fd\u6570\u5728x0\u5904\u624d\u53ef\u5bfc
错误；函数f(x)=0，定义域为非零实数，x0=0。
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