The formula for area is πr². Radius is circle \( \frac{diameter}{2} \):

r = \( \frac{d}{2} \)
r = \( \frac{8}{2} \)
r = 4
a = πr²
a = π(4²)
a = 16π

The entire length of this line is represented by AD which is AB + BD:

AD = AB + BD

The surface area of a cube is (2 x length x width) + (2 x width x height) + (2 x length x height):

sa = 2lw + 2wh + 2lh
sa = (2 x 9 x 1) + (2 x 1 x 1) + (2 x 9 x 1)
sa = (18) + (2) + (18)
sa = 38

The first step to solve a quadratic equation that's set to zero is to factor the quadratic equation:

b² + 3b - 40 = 0
(b - 5)(b + 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (b - 5) or (b + 8) must equal zero:

If (b - 5) = 0, b must equal 5
If (b + 8) = 0, b must equal -8

So the solution is that b = 5 or -8

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

p = x + y + z
p = 9cm + 9cm + 15cm = 33cm