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).

The sum of the interior angles of a triangle is 180°:
180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 20° - 41° = 119°

The Pythagorean theorem defines the relationship between the side lengths of a right triangle. The length of the hypotenuse squared (c²) is equal to the sum of the two perpendicular sides squared (a² + b²): c² = a² + b² or, solved for c, \(c = \sqrt{a + b}\)

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.

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

z² + 4z - 12 = 0
(z - 2)(z + 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 2) or (z + 6) must equal zero:

If (z - 2) = 0, z must equal 2
If (z + 6) = 0, z must equal -6

So the solution is that z = 2 or -6