观察下面三行数：2,-4,8,-16,32,-64,...；① 4,-2,10,-14,34,-62...；②

题目

观察下面三行数：2,-4,8,-16,32,-64,...；① 4,-2,10,-14,34,-62...；②
观察下面三行数：①2,-4,8,-16,32,-64,...；
② 4,-2,10,-14,34,-62...
③1,-2,4,-8,16,-32,...
写出每行第五十个数
要有列式

答案

1 [ (-1)^(n+1)] 2^n
2.
3 [ (-1)^(n-1)] 2^(n-1)
前面的控制符号,后边的控制数的变化