Hi Shal,
A shortcut method for finding the negative no of a binary is
"Starting from the right i.e LSB (Least Significant Bit) you find the first one bit. From LSB till the first 1 bit, including the 1 bit keep all the bits as it is and after the 1 bit interchange all other bit 1s to 0s and 0s to 1s"
eg;
x=001010
from right keep 10 as it is
remaining part 0010 - interchanging 0s to 1s and 1s to 0s we get 1101
combining the above 2 steps we get
-x=110110