To multiply monomials, multiply the coefficients (the numbers that come before the variables) of each term, add the exponents of like variables, and multiply the different variables together.

(8a)(6ab) - (7a²)(2b)
(8 x 6)(a x a x b) - (7 x 2)(a² x b)
(48)(a¹⁺¹ x b) - (14)(a²b)
48a²b - 14a²b
34a²b

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

y² - 9y + 18
y² + (-6 - 3)y + (-6 x -3)
(y - 6)(y - 3)

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).

You need to find the value of b so solve the first equation in terms of y:

4b + y = -7
y = -7 - 4b

then substitute the result (-7 - 4b) into the second equation:

5b - 2(-7 - 4b) = -1
5b + (-2 x -7) + (-2 x -4b) = -1
5b + 14 + 8b = -1
5b + 8b = -1 - 14
13b = -15
b = \( \frac{-15}{13} \)
b = -1\(\frac{2}{13}\)

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

sa = 2πr² + 2πrh
sa = 2π(1²) + 2π(1 x 9)
sa = 2π(1) + 2π(9)
sa = (2 x 1)π + (2 x 9)π
sa = 2π + 18π
sa = 20π