The relation {(-5, 5), (-6, 7), (-7, 7), (-8, 0)} is a function.
true
false

In a function, every input has one and only one output. 
if -5 is your input, then 5 is the output
if 8 is your input, then 0 is your output

multiple inputs can lead to the same output, like 
-6 as the input can give an output of 7
and also -7 as the input can give an output of 7

however, multiple one input cant not have multiple outputs. 
since none of those values share the same x values with different y values, the relation is in fact a function. 

the answer should be true

The answer is 8 apex