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.

A line segment is a portion of a line with a measurable length. The midpoint of a line segment is the point exactly halfway between the endpoints. The midpoint bisects (cuts in half) the line segment.

The entire length of this line is represented by AD which is AB + BD:

AD = AB + BD

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 -20 as well and sum (Inside, Outside) to equal -1. For this problem, those two numbers are -5 and 4. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - y - 20
y² + (-5 + 4)y + (-5 x 4)
(y - 5)(y + 4)

To multiply binomials, use the FOIL method. FOIL stands for First, Outside, Inside, Last and refers to the position of each term in the parentheses:

(y + 9)(y + 7)
(y x y) + (y x 7) + (9 x y) + (9 x 7)
y² + 7y + 9y + 63
y² + 16y + 63