// 编程序 用迭代法求a的立方根,求立方根的迭代公式为 ::Xi+1=（2*Xi）/3+a/(3*Xi*Xi) 假定X的初值为a,迭代到|Xi+1-Xi|<10的-5次方为止. 显示a=3,27的值,并通过调用pow(a,1.0/3)函数加以验证.。-//Compile a program with Iteration Method and the cube root, find the cube root of the iteration formula is:: Xi+1 = (2*