Here is a picture of the graph.
Proofs are... well... just that. They are your proof for why a certain property works or what you did to show your work. So essentially, you just do math like normal, a proof is showing what you did and why it works.
900, just 900 very just 900
Plug in -3 for x
f(-3) = 2(-3) - (-3 + 6)
f(-3) = -6 - (3)
f(-3) = -9
Solution: f(-3) = -9
