Умножаем и числитель и знаменатель на
sqrt(3+x+x^2)+sqrt(9-2x+x^2)
получаем
(sqrt(3+x+x^2)+sqrt(9-2x+x^2))*(sqrt(3+x+x^2)-sqrt(9-2x+x^2))/(x^2-3x+2)*(sqrt(3+x+x^2)+sqrt(9-2x+x^2))=
по формуле (a-b)*(a+b)=a^2-b^2
=(3+x+x^2-(9-2x+x^2))/((x^2-3x+2)*(sqrt(3+x+x^2)+sqrt(9-2x+x^2)))
=(3x-6)/((x-2)(x-1)*(sqrt(3+x+x^2)+sqrt(9-2x+x^2)))
сокращаем на (х-2)
lim_(x→2)(sqrt(3+x+x^2)+sqrt(9-2x+x^2))/(x^2-3x+2)=
=lim_(x→2)3/((x-1)*(sqrt(3+x+x^2)+sqrt(9-2x+x^2)))= 3/((2-1)*(3+3))=3/6=1/2