Irrational numbers are numbers which continue forever without repeating themselves if written as a decimal, for example: pi, root 2.
therefore, for no.6 2 1/8 = rational because it can be written as 2.125; -9 = rational; root 2 = irrational; root 9 = 3 so it is a rational number; 11/8 =1.375 exactly so is rational
