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).

An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite:

d° = b° + c°

To find angle c, remember that the sum of the interior angles of a triangle is 180°:

180° = a° + b° + c°
c° = 180° - a° - b°
c° = 180° - 42° - 40° = 98°

So, d° = 40° + 98° = 138°

A shortcut to get this answer is to remember that angles around a line add up to 180°:

a° + d° = 180°
d° = 180° - a°
d° = 180° - 42° = 138°

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.

A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

z² - 3z + 13 = 3z + 5
z² - 3z + 13 - 5 = 3z
z² - 3z - 3z + 8 = 0
z² - 6z + 8 = 0

Next, factor the quadratic equation:

z² - 6z + 8 = 0
(z - 2)(z - 4) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 2) or (z - 4) must equal zero:

If (z - 2) = 0, z must equal 2
If (z - 4) = 0, z must equal 4

So the solution is that z = 2 or 4