Question

What is the input if the output is 0 ?

Answer 1

In other words, what is y if x is 0.

Look on the graph, a line passes through point, $A(x,y)\longrightarrow A(0,-3)$

So we can conclude that at that very point the input x was 0 and the output y was -3 therefore,

$\boxed{f(-3)=0}$

Hope this helps.

r3t40