A circle is a figure in which each point around its perimeter is an equal distance from the center. The radius of a circle is the distance between the center and any point along its perimeter. A chord is a line segment that connects any two points along its perimeter. The diameter of a circle is the length of a chord that passes through the center of the circle and equals twice the circle's radius (2r).

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 7 x 4
a = 28

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

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.

(5a)(8ab) - (9a²)(6b)
(5 x 8)(a x a x b) - (9 x 6)(a² x b)
(40)(a¹⁺¹ x b) - (54)(a²b)
40a²b - 54a²b
-14a²b