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(x) fmax?f(?2)??16a?5??11??a?b
?f(x)?x3?2x2?5
②当a?0时f(x)在[?2,0)? 在(0,1]?
(x) fmin?f(0)?b??11
当a?0时，f(?2)??16a?b??a?b?f(1)
(x) fmax?f(?2)??16a?6?5?a??1
?f(x)??x3?2x2?11
即f(x)?x3?2x2?5或f(x)??x3?2x2?11
b2x2?2x?b??0 ⑵f?(x)?2x?x?1x?1 设g(x)?2x?2x?b
2由题意知g(x)?0在(?1,??)有两相异实根
????4?8b?0?1g(?1)?b?0?0?b? ?2?1?x???0?2即b的取值范围是(0,)
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