How to match function input to output given the graph (example) | Algebra I | Khan Academy

Sal finds the input value for which g(x)=-2 given the graph of g.

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[gsynth]

0:37 - What tells you that this graph is y=g(x)? What visual cue gives that away? I figure it's something obvious, but I don't know what to look for.

[exliesaturn]

how did you exactly get -9? i understand it well but i'm a little lost