1.　　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.。

-Programmed iterative method to find the cube root and cube root iteration formula :: Xi+1 = (2* Xi)/3+ a/(3* Xi* Xi)

Assumed that the initial value of X for a, a = 3,27 of value iteration | Xi+1- Xi | <10 epsilon., And be verified by calling pow (a, 1.0/3) function. .