To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

2a + 6a = 8a

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).

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 -4. 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, -9) so the slope becomes:

Plugging these values into the slope-intercept equation:

y = -2\(\frac{1}{2}\)x - 4

To factor a quadratic expression, apply the FOIL method (First, Outside, Inside, Last) in reverse. First, find the two Last terms that will multiply to produce -24 as well and sum (Inside, Outside) to equal 5. For this problem, those two numbers are -3 and 8. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 5y - 24
y² + (-3 + 8)y + (-3 x 8)
(y - 3)(y + 8)

The area of a parallelogram is equal to its length x width:

a = l x w
a = a x b
a = 1 x 9
a = 9