Answer:
Top two are functions bottom two are not, functions can only have one outpur for each input, or one y value for each x value.
Explanation:
functions can only have one one output for every input. this means on a graph if you draw a vertical line if the graph touches that line in two places it is not a function, so the lower left graph is not a function.
if you only hae points or ordered pairs like the lower right part of the picture you have to make sure that each x value is only matched up with 1 y value. so there is (3, 3) and (3,9) both have the input (x value) of 3 but one has an output (y value) of 3 ad the other has 9, so one input has multiple outputs, or if you prefer one x value coresponds to multiple y values. Either way is correct.
Important to say multiple inputs can have the same output. For instance x^2 has both -2 and 2 as inputs have 4 as outputs, but it is still a function. if it had 2 correspond to BOTH 4 and -4 or something else then it would not be a function.