Difference Method For Several Singularly Perturbed Problems

This paper is divided into two parts,in the first part,we proposed on aneffective solution method to solve a class of singularly perturbed third ordersystem of equations,first using the superposition principle of linear equationsand Maximum principle,the system of third order singularly perturbed equationsis approximately decomposed into a system of singularly perturbed second orderequations and a system of first order ordinary differential equations．then weobtain the error estimate analysis between the exact solution and approximatesolution by using the Maximum principle Finally,difference scheme of solvingsecond order equations was given,then use the Maximum principle obtain theerror estlmateThe second part,we give the difference scheme of soving singularly perturbedfourth order equation on shishkin type of meshes,and we obtain error estimateof funciton and first derivative,second derivative by using Maximum principle.