A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 1 + 8 + 4 + 2
p = 15

The slope of this line is the change in y divided by the change in x. The endpoints of this line segment are at (-2, -4) and (2, 4) so the slope becomes:

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 - 84 = -3z - 3
z² - 3z - 84 + 3 = -3z
z² - 3z + 3z - 81 = 0
z² - 81 = 0

Next, factor the quadratic equation:

z² - 81 = 0
(z - 9)(z + 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 9) or (z + 9) must equal zero:

If (z - 9) = 0, z must equal 9
If (z + 9) = 0, z must equal -9

So the solution is that z = 9 or -9

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).