The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 9cm + 15cm + 7cm = 31cm

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.

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).

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

7a⁴ + 2a⁴ = 9a⁴

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