9.设y(x)、y2(x)是二阶齐次线性方程y"+p(x)+qx)=0的两 个解,令 x)y2( W(x)=(x)y2(x)=H(x)y2(x)-y(x)2(x), 证明 (1)W(x)满足方程W+p(x)W0 (2)/(x)=W(xn)k2J2P0t