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

For parallel lines with a transversal, the following relationships apply:

• angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°)
• alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°)
• all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other
• same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°)

Applying these relationships starting with d° = 160, the value of c° is 20.

A trapezoid is a quadrilateral with one set of parallel sides.

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

c² - 11c + 1 = -5c - 4
c² - 11c + 1 + 4 = -5c
c² - 11c + 5c + 5 = 0
c² - 6c + 5 = 0

Next, factor the quadratic equation:

c² - 6c + 5 = 0
(c - 1)(c - 5) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c - 1) or (c - 5) must equal zero:

If (c - 1) = 0, c must equal 1
If (c - 5) = 0, c must equal 5

So the solution is that c = 1 or 5

To solve this equation, isolate the variable for which you are solving (c) on one side of the equation and put everything else on the other side.

-8c + 9z = 6c + 7z + 8
-8c = 6c + 7z + 8 - 9z
-8c - 6c = 7z + 8 - 9z
-14c = -2z + 8
c = \( \frac{-2z + 8}{-14} \)
c = \( \frac{-2z}{-14} \) + \( \frac{8}{-14} \)
c = \(\frac{1}{7}\)z - \(\frac{4}{7}\)