Unit digit of a square of a number is equal to the unit digit of square of unit digit of that number. So, (i)81 - Unit digit of square of 81 will be 1 . (ii)272 - Unit digit of square of 272 will be 4 . (iii)799 - Unit digit of square of 799 will be 1 . (iv)3853 - Unit digit of square of 3853 will be 9 . (v)1234 - Unit digit of square of 1234 will be 6 . (vi)26387 - Unit digit of square of 26387 will be 9 . (vii)52698 - Unit digit of square of 52698 will be 4 . (viii)99880 - Unit digit of square of 99880 will be 0 . (ix)12796 - Unit digit of square of 12796 will be 6 . (x)55555 - Unit digit of square of 55555 will be 5
distribute the -3 and the square into the first equation multiply the second equation by 2 add the equations together factor out -3 factor inside parenthesis refine