A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

The slope-intercept equation for a line is y = mx + b where m is the slope and b is the y-intercept of the line. From the graph, you can see that the y-intercept (the y-value from the point where the line crosses the y-axis) is 3. 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, -1) and (2, 7) so the slope becomes:

Plugging these values into the slope-intercept equation:

y = 2x + 3

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 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.

a + 7 = \( \frac{a}{-7} \)
-7 x (a + 7) = a
(-7 x a) + (-7 x 7) = a
-7a - 49 = a
-7a - 49 - a = 0
-7a - a = 49
-8a = 49
a = \( \frac{49}{-8} \)
a = -6\(\frac{1}{8}\)

The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².