To find if a graph is a function you can use the vertical line test. The vertical line test is where you place a vertical (up and down) line on the graph. If this vertical line intersects the graph more then once it is NOT a function. It is a relation. Another way to see if it is NOT a function is seeing if there are coordinates where they have the same x-value but different y-values
Graph 1: You were correct. This is NOT a function because the vertical line would cross the graph two times
Graph 2: You were correct. This is NOT a function, because there are three points that have the x-value of -4 yet the have different y-values
Graph 3: This actually is a function! It passes the vertical line test. Although there are two points that have the y-value of -2, that's okay. There are no points with the same x-value
Graph 4: You are correct. This kind of graph is called a piecewise function. It does look like there are two points that have the same x-value, but since only one circle is colored in it means that only the colored in point is "valid."
Graph 5: You are correct. This IS a function. It passes the vertical line test.
Graph 6: This is NOT a function. If you put a vertical line through the circle you will hit it at the top and at the bottom
Hope this helped!
~Just a girl in love with Shawn Mendes