Is the set of multiples of 4 closed under addition? explain why or provide a counterexample if not.

a. yes, because the sum of any two multiples of 4 is also a multiple of 4.

b. yes, because the sum of any two multiples of 4 is also a multiple of 8.

c. no, and a counterexample is –4 + (–8) = –12.

d. no, and a counterexample is 26 + 16 = 42.

Do some research and find a city that has experienced population growth. determine its population on january 1st of a certain year. write an exponential function to represent the city’s population, y, based on the number of years that pass, x after a period of exponential growth. describe the variables and numbers that you used in your equation.

Sally deposited money into a savings account paying 4% simple interest per year.the first year,she earn $75 in interest.how much interest will she earn during the following year?

From the top of a tree a bird looks down on a field mouse at an angle of depression of 50°. if the field mouse is 40 meters from the base of the tree, find the vertical distance from the ground to the bird's eyes.