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

Angles around a line add up to 180°. Angles around a point add up to 360°. When two lines intersect, adjacent angles are supplementary (they add up to 180°) and angles across from either other are vertical (they're equal).

A monomial contains one term, a binomial contains two terms, and a polynomial contains more than two terms.

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

sa = 2πr² + 2πrh
sa = 2π(9²) + 2π(9 x 8)
sa = 2π(81) + 2π(72)
sa = (2 x 81)π + (2 x 72)π
sa = 162π + 144π
sa = 306π

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 -56 as well and sum (Inside, Outside) to equal -1. For this problem, those two numbers are -8 and 7. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² - y - 56
y² + (-8 + 7)y + (-8 x 7)
(y - 8)(y + 7)