What is the surface area of a sphere with radius 2

Logan wants to know how many skateboards have defective parts. he inspects 20,000 skateboards and keeps track of the number of defects per board. use his probability distribution table to find the expected value for defects on a skateboard.

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?

Xy x xy if a and b are positive integers such that a*b=9 and b*a=72 what is the value of a/b