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 area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(6 + 4)(4)
a = ½(10)(4)
a = ½(40) = \( \frac{40}{2} \)
a = 20

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 - 13z + 9 = -5z - 3
z² - 13z + 9 + 3 = -5z
z² - 13z + 5z + 12 = 0
z² - 8z + 12 = 0

Next, factor the quadratic equation:

z² - 8z + 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

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).