计算:[x(xy2+2xy)-y(x2y-6x2y2)]÷2x2y.
原式=(x2y2+2x2y-x2y2+6x2y3)÷2x2y=(2x2y+6x2y3)÷2x2y=1+3y2.
扩张型心肌病的超声心电图特征有哪些?