The formula for circumference is circle diameter x π:

c = πd
c = 13π

To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(6a)(5ab) - (4a²)(6b)
(6 x 5)(a x a x b) - (4 x 6)(a² x b)
(30)(a¹⁺¹ x b) - (24)(a²b)
30a²b - 24a²b
6a²b

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce 48 as well and sum (Inside, Outside) to equal 14. For this problem, those two numbers are 6 and 8. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 14y + 48
y² + (6 + 8)y + (6 x 8)
(y + 6)(y + 8)

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.

A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.