Solution (Question 4): √√ (N2+N)-N = n/[√ (N2+N)+N] =1[√ (1+N)+65438+.

Solution (Question 7):∫x→∞, f (x) = ax+(b-a-1)+c/(1+x 2), where c is a constant, if a≠0, b-a-652. ∴a=0,b= 1。 For reference.