The volume of a cylinder is πr²h:

v = πr²h
v = π(9² x 8)
v = 648π

You need to find the value of a so solve the first equation in terms of x:

8a + x = -1
x = -1 - 8a

then substitute the result (-1 - 8a) into the second equation:

-7a + 8(-1 - 8a) = 8
-7a + (8 x -1) + (8 x -8a) = 8
-7a - 8 - 64a = 8
-7a - 64a = 8 + 8
-71a = 16
a = \( \frac{16}{-71} \)
a = -\(\frac{16}{71}\)

The perimeter of a triangle is the sum of the lengths of its sides:

p = x + y + z
p = 13cm + 6cm + 7cm = 26cm

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).

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 - 7)(y + 1)
(y x y) + (y x 1) + (-7 x y) + (-7 x 1)
y² + y - 7y - 7
y² - 6y - 7