ANSWER
• Even degree
,
• Negative coefficient
EXPLANATION
When the degree is even, both ends of the graph point to the same direction - both up or both down. If the degree is odd, one end points up and the other points down.
When the coefficient is negative and the degree is even the ends of the graph point down. If it's positive, the ends point up.
If the degree is even you can think of a happy face for positive coefficient and a sad face for a negative coefficient:
