matlab的基本实现函数有图 例如求代数方程3x5+4x4+7x3+2x2+9x+12=0的所有根。（利用roots函数）-The basic realization of matlab function has a plan such as the algebraic equation 3x5+4 x4+7 x3+2 x2+9 x+12 = 0 for all roots. (Using the roots function)