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).

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

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.

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 + 8)(y + 7)
(y x y) + (y x 7) + (8 x y) + (8 x 7)
y² + 7y + 8y + 56
y² + 15y + 56

To solve this equation, isolate the variable for which you are solving (b) on one side of the equation and put everything else on the other side.

-5b - 2z = -2b - 5z - 5
-5b = -2b - 5z - 5 + 2z
-5b + 2b = -5z - 5 + 2z
-3b = -3z - 5
b = \( \frac{-3z - 5}{-3} \)
b = \( \frac{-3z}{-3} \) + \( \frac{-5}{-3} \)
b = z + 1\(\frac{2}{3}\)