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.

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

The surface area of a cylinder is 2πr² + 2πrh:

sa = 2πr² + 2πrh
sa = 2π(1²) + 2π(1 x 4)
sa = 2π(1) + 2π(4)
sa = (2 x 1)π + (2 x 4)π
sa = 2π + 8π
sa = 10π

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 -54 as well and sum (Inside, Outside) to equal 3. For this problem, those two numbers are -6 and 9. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 3y - 54
y² + (-6 + 9)y + (-6 x 9)
(y - 6)(y + 9)

The area of a rectangle is equal to its length x width:

a = l x w
a = a x b
a = 3 x 4
a = 12