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.

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 -15 as well and sum (Inside, Outside) to equal -2. For this problem, those two numbers are -5 and 3. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 2y - 15
y² + (-5 + 3)y + (-5 x 3)
(y - 5)(y + 3)

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

p = x + y + z
p = 10cm + 6cm + 12cm = 28cm

A rhombus is a parallelogram with four equal-length sides. A square is a rectangle with four equal-length 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, 4) and (2, 2) so the slope becomes:

Plugging these values into the slope-intercept equation:

y = -\(\frac{1}{2}\)x + 3