F(x) = {log - log7/x - 7 ,for x ≠7 ;at x =7
7. ,for x =7
if s= {a,b,c,d} where a={ }, b={a,b}, c={a,c} and d={a,b,c}. show that u is a binary operation on s but n is not
In how many ways 5 boys and 5 girls may be arranged around a table so that no two girls sit together?