常数除以减函数得？常数除以增函数得？增函数除以常数？减函数除以常数？ 增函数除以增函数是减函数还是增函数要是一除以增函
\u51cf\u51fd\u6570\u9664\u4ee5\u51cf\u51fd\u6570\uff0c\u589e\u51fd\u6570\u9664\u4ee5\u589e\u51fd\u6570\uff0c\u51cf\u51fd\u6570\u9664\u4ee5\u589e\u51fd\u6570\uff1f\u6c42\u95ee\u4e0d\u786e\u5b9a\u3002
\u4f8b\u5982f(x)=1/x\uff0cg(x)=x
\u5546\u65e2\u6709\u589e\uff0c\u53c8\u6709\u51cf\u3002
\u589e\u51fd\u6570\u9664\u4ee5\u589e\u51fd\u6570
\u65e2\u6709\u53ef\u80fd\u662f\u589e\u51fd\u6570
\u4e5f\u53ef\u80fd\u662f\u51cf\u51fd\u6570
\u800c\u4e00\u9664\u4ee5\u589e\u51fd\u6570\u7684\u8bdd
\u4e00\u5b9a\u662f\u51cf\u51fd\u6570
后两者很显然：增函数除以正（负）常数是增（减）函数。减函数除以正（负）常数是减（增）函数。
前两者很复杂：不仅涉及常数的符号，而且涉及函数的符号。举例
-x单减，1/x分段单减：
2÷（-x)=-2/x,分段单增；2÷（1/x)=2x（x≠0）单增；
-2÷（-x)=2/x,分段单减；-2÷（1/x)=-2x（x≠0）单减。
x^2+x两个单区，常数乘以它以后变为4个单区啊！
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