Log of negative numbers is not defined.

For antilog of negative numbers write the number x as [x] + {x}

Here, [x] will give you the exponent to the base 10 and antilog of {x} found using

antilog table will give you coefficient.

Given, antilog (-9.7) = antilog (-10 + 0.3)

                                =  2 * 10^-10            {since log 2 = 0.301, antilog(0.301)=2}