f(x)=x2-ax+3,x is rational 2-x,x is rational  . Is continuous exactly at two points then a∈

fx=x2−ax+3     , x is rational2−x              , x is rational Is continuous when x2-ax+3=2-x or x2-(a-1)x+1=0 which must have two distinct roots  for (a-1)2-4>0⇒a∈(-∞,-1)∪(3,∞)⇒a∈−∞,−1∪3,∞