然后开根号得到7，再加7。

Then, square root to 7, and add 7 more.

但是你可以通过对49开根号得到7。

However, you could get to 7 by reaching 49 first.

所以你在2的基础上加7得到9，然后开根号。

So you add 7 to get to 9, then take the square root again.

因为工作的需要，要在单片机上实现开根号的操作。

Because the work needs to realize single-chip on the operation of open radical sign .

对9和25开根号会带来不错的结果，但是无法从2得到25。

Taking the square root of 9 or 25 would get you to a good place, but it turns out that 25 is unreachable from 2.