单项选择题A.<br ><img src= {$uploaddir} b19fbe5a-0698-43f4-85f7-455676118f34.jpg >B.<br ><img src= {$uploaddir} 2e7d2f3e-99dc-4d33-a40c-b0ffe6878eff.jpg >C.<br ><img src= {$uploaddir} dfd9962e-c70e-485a-8a25-541a2634bab4.jpg >D.<br ><img src= {$uploaddir} 89cd64a0-6c4a-4403-9c67-cdc10d091fd6.jpg >
单项选择题A.<br ><img src= {$uploaddir} 92dbb032-09c5-422d-bd0c-b5177932a98a.jpg >B.0C.<br ><img src= {$uploaddir} 38c26429-7afd-46f1-8b8b-436738b18cdb.jpg >D.<br ><img src= {$uploaddir} 53c311f0-7a31-420d-8d6b-0e0f60729271.jpg >
单项选择题A.<br ><img src= {$uploaddir} a7857777-74e8-41cd-b477-fe3417670841.jpg >B.<br ><img src= {$uploaddir} f68468f7-d5f1-4515-a2ba-5efda1056100.jpg >C.<br ><img src= {$uploaddir} b5d1e5d8-5266-49db-ab55-3f5e890efbe6.jpg >D.0
单项选择题A.<br ><img src= {$uploaddir} d98972e6-cd5c-4a79-b4a7-669a2e2de6a8.jpg >B.3C.<br ><img src= {$uploaddir} cde43d4f-b702-485d-8fa5-1e1167fbfe30.jpg >D.不存在
单项选择题函数f(x)=x3=3x2的拐点是( ).