The circumference of a circle is the distance around its perimeter and equals π (approx. 3.14159) x diameter: c = π d. The area of a circle is π x (radius)² : a = π r².

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 8 x 3) + (2 x 3 x 1) + (2 x 8 x 1)
sa = (48) + (6) + (16)
sa = 70

To solve this equation, replace the variables with the values given and then solve the now variable-free equation. (Remember order of operations, PEMDAS, Parentheses, Exponents, Multiplication/Division, Addition/Subtraction.)

6a(a - x)
6(-3)(-3 + 3)
6(-3)(0)
(-18)(0)
0

A cylinder is a solid figure with straight parallel sides and a circular or oval cross section with a radius (r) and a height (h). The volume of a cylinder is π r²h and the surface area is 2(π r²) + 2π rh.

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

b² - 8b - 9 = 0
(b + 1)(b - 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (b + 1) or (b - 9) must equal zero:

If (b + 1) = 0, b must equal -1
If (b - 9) = 0, b must equal 9

So the solution is that b = -1 or 9