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 rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s²).

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

c - 2x = -7c + x - 9
c = -7c + x - 9 + 2x
c + 7c = x - 9 + 2x
8c = 3x - 9
c = \( \frac{3x - 9}{8} \)
c = \( \frac{3x}{8} \) + \( \frac{-9}{8} \)
c = \(\frac{3}{8}\)x - 1\(\frac{1}{8}\)

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 5 x 2) + (2 x 2 x 7) + (2 x 5 x 7)
sa = (20) + (28) + (70)
sa = 118

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 -36 as well and sum (Inside, Outside) to equal 5. For this problem, those two numbers are -4 and 9. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 5y - 36
y² + (-4 + 9)y + (-4 x 9)
(y - 4)(y + 9)