含参数的一元二次不等式专题.pdf
周潭中学-周根虎经典案例分析一二次项系数为常数例 1、解关于 x的不等式:.0)2(2axax解:0)2(2axax)(3243240422aaaa或,此时两根为242)2(21aaax,242)2(22aaax.(1)当324a时,0,)(解集为(248)2(,2aaa)(,248)2(2aaa);(2)当324a时,0,)(解集为(13,)(,13);(3)当324324a时,0,)(解集为R;(4)当324a时,0,)(解集为(13,)(,13);(5)当324a时,0,)(解集为(248)2(,2aaa)(,248)2(2aaa).二二次项系数含参数例 2、解关于 x的不等式:.01)1(2xaax解:若0a,原不等式.101xx若0a,原不等式axxax10)1)(1(或.1x若0a,原不等式.0)1)(1(xax)(文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2其解的情况应由a1与 1 的大小关系决定,故(1)当1a时,式)(的解集为;(2)当1a时,式)(11xa;(3)当10a时,式)(ax11.综上所述,当0a时,解集为 11xaxx或;当0a时,解集为 1xx;当10a时,解集为 axx11;当1a时,解集为;当1a时,解集为 11xax.例 3、解关于 x的不等式:.012axax解:.012axax)((1)0a时,.01)(Rx(2)0a时,则0042aaa或4a,此时两根为aaaax2421,aaaax2422.当0a时,0,)(xaaaa242aaaa242;当04a时,0,Rx)(;当4a时,0,21)(xRx且;当4a时,0,)(或aaaax242aaaax242.综上,可知当0a时,解集为(aaaa242,aaaa242);当04a时,解集为R;当4a时,解集为(21,)(,21);当4a时,解集为(aaaa24,2)(,242aaaa).文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 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4、解不等式)0(01)1(2axaax分析:此不等式可以分解为:0)1(axax,故对应的方程必有两解。本题只需讨论两根的大小即可。解:原不等式可化为:0)1(axax,令aa1,可得:1a当1a或10a时,aa1,故原不等式的解集为axax1|;当1a或1a时,aa1,可得其解集为;当01a或1a时,aa1,解集为axax1|。例 5、解不等式06522aaxx,0a解 原不等式可化为:0)3(2axax,对应方程0)3(2axax的两根为axax3,221,当a0 时,解 集 为axaxx23|或;当0a时,解 集 为|23x xaxa或相关练习训练1、解不等式Rmxxm0141222、解不等式042axx3、解关于x的不等式:033)1(22axxa文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 ZE4D9Q7A8F2文档编码:CL5U10Y3X3F1 HQ6T7L7U1J7 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