Question

-4x-2y=16 is it increasing or decreasing

Answer 1

Well you want to find if   Y is increasing or decreasing it is actually supposed to be like this 
-4x-2y=16
+4x       +4x
-2y=4x+16
-2/-2 4/-2 16/-2
y=-2 + -8

Answer 2

 Function values can be positive or negative, and they can increase or decrease as the input increases. Well positive means that the value of the function is greater than zero.