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

p = x + y + z
p = 14cm + 15cm + 12cm = 41cm

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 -9 as well and sum (Inside, Outside) to equal 0. For this problem, those two numbers are -3 and 3. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - 9
y² + (-3 + 3)y + (-3 x 3)
(y - 3)(y + 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.

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 cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.