编写一个求方程ax2 + bx + c = 0的根 的程序，用3个函数分别求当b2-4ac大于零、等于零、和小于零时的方程的根。要求从主函数输入a,b,c的值并输出结果。 -Write an equation for ax2+ bx+ c = 0 root of procedures, the use of three function for respectively when b2-4 ac greater than zero, zero, and less than zero hour of the root of the equation. Requirements from the main function input a, b, c and the value of the output.