A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

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

a = l x w
a = a x b
a = 5 x 8
a = 40

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 - 5)(y - 2)
(y x y) + (y x -2) + (-5 x y) + (-5 x -2)
y² - 2y - 5y + 10
y² - 7y + 10

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-3x - 7 = -9 + 6x
-3x = -9 + 6x + 7
-3x - 6x = -9 + 7
-9x = -2
x = \( \frac{-2}{-9} \)
x = \(\frac{2}{9}\)

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².