Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 8 + 9 + 2 + 8
p = 27

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).

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).

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.

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

z² - 2z - 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