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.

(2a)(9ab) - (9a²)(3b)
(2 x 9)(a x a x b) - (9 x 3)(a² x b)
(18)(a¹⁺¹ x b) - (27)(a²b)
18a²b - 27a²b
-9a²b

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.

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 6 + 1 + 9 + 3
p = 19

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses.