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.

2a³ - 8a³ = -6a³

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:

(y + 2)(y + 7)
(y x y) + (y x 7) + (2 x y) + (2 x 7)
y² + 7y + 2y + 14
y² + 9y + 14

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

p = x + y + z
p = 13cm + 6cm + 5cm = 24cm

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 x 4b = (2 x 4) (a x b) = 8ab

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).