Coba jelasin maxx in R 2x dari Optimisasi (matematik) dalam bahasa sunda dong

This asks for the maximum value for the expression 2x, where x ranges over the réals. In this case, there is no such maximum as the expression is unbounded, so the answer is "infinity" or "undefined".

arg minx in [-∞,-1]   x2+1

This asks for the value(s) of x in the interval [-∞,-1] which minimizes the expression x2+1. (The actual minimum value of that expression does not matter.) In this case, the answer is x = -1.

arg maxx in [-∞,5], y in R   x · cos(y)

This asks for the (x,y) pair(s) that maximize the value of the expression x·cos(y), with the added constraint that x cannot exceed 5. (Again, the actual maximum value of the expression does not matter.) In this case, the solutions are the pairs of the form (5,2πk) and (-5,(2k+1)π), where k ranges over all integers.