The answer is in the graph
Answer:

Step-by-step explanation:
To use the least number of terms, simplify the expression. To simplify, distribute into the parenthesis and combine like terms.

Only 25 and 28 are functions.
A function must have only one y value per x value. For 26, the y value of 0 and multiple others have two different y values. For 27, all x values less than 0 have multiple y values.
In a triangle when an angle between two equal length sides is 60 that means that the triangle is equilateral.