The formula for area is πr². Radius is circle \( \frac{diameter}{2} \):

r = \( \frac{d}{2} \)
r = \( \frac{6}{2} \)
r = 3
a = πr²
a = π(3²)
a = 9π

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

a = l x w
a = a x b
a = 7 x 8
a = 56

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 + 4)(y + 7)
(y x y) + (y x 7) + (4 x y) + (4 x 7)
y² + 7y + 4y + 28
y² + 11y + 28

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length sides.

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).