The formula for circumference is circle diameter x π:

c = πd
c = 12π

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(6 + 5)(3)
a = ½(11)(3)
a = ½(33) = \( \frac{33}{2} \)
a = 16\(\frac{1}{2}\)

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

x² + x - 72 = 0
(x - 8)(x + 9) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (x - 8) or (x + 9) must equal zero:

If (x - 8) = 0, x must equal 8
If (x + 9) = 0, x must equal -9

So the solution is that x = 8 or -9

To combine like terms, add or subtract the coefficients (the numbers that come before the variables) of terms that have the same variable raised to the same exponent.

6a⁴ + 9a⁴ = 15a⁴

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 - 1)(y + 4)
(y x y) + (y x 4) + (-1 x y) + (-1 x 4)
y² + 4y - y - 4
y² + 3y - 4