Find a so that the point (-1,2) is on the graph of f(x)=ax^2 +4

Terri makes a quilt using three sizes of fabric squares the side lenght of each fabric square is the square root of the area

Monthly water bills for a city have a mean of $108.43 and a standard deviation of $32.09. find the probability that a randomly selected bill will have an amount greater than $155, which the city believes might indicate that someone is wasting water. would a bill that size be considered unusual?

What is always true when two whole numbers are subtracted?