Find the absolute maximum value and the absolute minimum value,

f(x)= (x +1 )/ (x-1) on [2, 4]

f'(x) = (x-1 - (x+1) )/(x-1)^2 = -2/(x-1)^2

= 0 for a max/min

no solution
so look at the endpoints:
f(2) = 3/1 = 3
f(4) = 5/3

the min is 5/3, the max is 3