Answer:
Step-by-step explanation:
1) f(x) = |x| has its vertex at (0, 0), so the x-value is 0.
2) Cannot figure out what you meant by \x{ + 3.
3) f(x) = 5x + 31 has a straight line graph, no vertex.
4) [x] - 6 does not have a vertex, or at least not a well-defined one like |x|
5) Unsure of what you meant by 5x + 31 - 6. Did you mean 5x + 25? This does not have a vertex.