Define the function f : 1 - 3 , - 2, - 1, 0, 1 , 2, 31 - 10, 1 , 4, 9 ) by f ( x ) = x2. ( a ) Is the function f injective ? ( b ) Is the function f

I believe that this function is True for all 3 elements but I only came to that conclusion by drawing a picture for it. What is the appropriate way to show a function proof like this?

Define the function f : 1 - 3 , - 2, - 1, 0, 1 , 2, 31 - 10, 1 , 4, 9 ) by f ( x ) = x2.( a ) Is the function f injective ?( b ) Is the function f surjective ?( C ) Is the function & bijective ?