Can yall please tell me if these are functions or not and explain why.

The graph shows the rate at which paint is used to paint a wall. enter values to complete each statement below based on the graph. when 1 gallon of paint has been used, ( # ) square feet of the wall will be painted. the unit rate is ( # )square feet per gallon.

If there is no real number solution to the quadratic equation x^2+2x+c=0 what is a possible value of c? 1 -2 0 3

Express the following as a function of a single angle. cos(60) cos(-20) - sin(60) sin(-20)