有函数f(x)=ex可展开成：f(0)+f’(0)x/1!+f”(0)x /2!+…。编写函数程序求ex，使误差小于0.0000001。(The function f (x) =ex can develop into: F (0) +f (0) "x/1! +f" (0) x + /2.... Write function program ex, so that the error is less than 0.0000001.)