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 area of a triangle is equal to ½ base x height:

a = ½bh
a = ½ x 2 x 6 = \( \frac{12}{2} \) = 6

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

a² + 6a - 16 = 0
(a - 2)(a + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 2) or (a + 8) must equal zero:

If (a - 2) = 0, a must equal 2
If (a + 8) = 0, a must equal -8

So the solution is that a = 2 or -8

The coordinate grid is composed of a horizontal x-axis and a vertical y-axis. The center of the grid, where the x-axis and y-axis meet, is called the origin.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 9 + 7 + 1 + 1
p = 18