Base conversion - Negative base?

The whole number portion remains the same !! The decimal portion is 5678/10000 as are all decimals i.e. 0.6 = 6/10 (note that the denominator is 2 digits to the numerators 1) : 0.78 = 78/100 & the 0.5678 is as shown ~~ these can be simplified by division ~~ in this case only by 2 equalling 1234 2839/5000