A trapezoid is a quadrilateral with one set of parallel sides.

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

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.

To find the diagonal we need to know the length of one of the square's sides. We know the area and the area of a square is the length of one side squared:

a = s²

so the length of one side of the square is:

s = \( \sqrt{a} \) = \( \sqrt{81} \) = 9

The Pythagorean theorem defines the square of the hypotenuse (diagonal) of a triangle with a right angle as the sum of the squares of the other two sides:

c² = a² + b²
c² = 9² + 9²
c² = 162
c = \( \sqrt{162} \) = \( \sqrt{81 x 2} \) = \( \sqrt{81} \) \( \sqrt{2} \)
c = 9\( \sqrt{2} \)

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-2x + 8 = \( \frac{x}{9} \)
9 x (-2x + 8) = x
(9 x -2x) + (9 x 8) = x
-18x + 72 = x
-18x + 72 - x = 0
-18x - x = -72
-19x = -72
x = \( \frac{-72}{-19} \)
x = 3\(\frac{15}{19}\)