x1+a1 x2+a1^2 x3=a1^3x1+a2 x2+a2^2 x3=a2^3x1+a3 x2+a3^2 x3=a3^3x1+a4 x2+a4^2 x3=a4^31.证明:若a1,a2,a3,a4两两互不相等,则此线性方程组无解2.若a1=a3=k a2=a4=-k k不等于0 求通解