平面曲线<img src="https://static.zxtiku.com/wangke/imgs/topic/47bc468f5630f658539e3aee845b5833.jpg"/>绕 x轴旋转所得的旋转曲面的方程为<img src="https://static.zxtiku.com/wangke/imgs/topic/b8fa93d46f109cc18a5f70a143f7d172.jpg"/>（）.