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°).

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

a² - 2a - 3 = 0
(a + 1)(a - 3) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a + 1) or (a - 3) must equal zero:

If (a + 1) = 0, a must equal -1
If (a - 3) = 0, a must equal 3

So the solution is that a = -1 or 3

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

p = x + y + z
p = 5cm + 7cm + 10cm = 22cm

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.

8a x 5b = (8 x 5) (a x b) = 40ab

You can only add or subtract monomials that have the same variable and the same exponent. For example, 2a + 4a = 6a and 4a² - a² = 3a² but 2a + 4b and 7a - 3b cannot be combined. However, you can multiply and divide monomials with unlike terms. For example, 2a x 6b = 12ab.