A line on the coordinate grid can be defined by a slope-intercept equation: y = mx + b. For a given value of x, the value of y can be determined given the slope (m) and y-intercept (b) of the line. The slope of a line is change in y over change in x, \({\Delta y \over \Delta x}\), and the y-intercept is the y-coordinate where the line crosses the vertical y-axis.

The formula for area is πr². Radius is circle \( \frac{diameter}{2} \):

r = \( \frac{d}{2} \)
r = \( \frac{6}{2} \)
r = 3
a = πr²
a = π(3²)
a = 9π

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.

9c - 5 = 7 - 8c
9c = 7 - 8c + 5
9c + 8c = 7 + 5
17c = 12
c = \( \frac{12}{17} \)
c = \(\frac{12}{17}\)

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 13cm + 13cm + 12cm = 38cm

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).