Which of the following is not equivalent to x - y + z?

x + z - y
z + x - y
y - x + z
z - y + x

question:

could we have options?

answer: evaluate the objective function at each vertex to determine which - and -values, if any, maximize or minimize the function. example: find the minimum value and maximum value of the objective function f ( x , y ) = 4 x + 5 y , subject to the following constraints