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

p = x + y + z
p = 8cm + 8cm + 13cm = 29cm

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).

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

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce 2 as well and sum (Inside, Outside) to equal 3. For this problem, those two numbers are 1 and 2. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 3y + 2
y² + (1 + 2)y + (1 x 2)
(y + 1)(y + 2)