Find all values of x at which the graph of
y = x²-4cox changes concavity on (-/2,/2).
1. x = -(/3)
2. x = (/6)
3. x = -(/6), (/6)
4. x = (/3)
5. there are no values of x
6. x = -(/3), (/3)
7. x = -(/6)