The formula for circumference is circle diameter x π:

c = πd
c = 6π

To solve this equation, repeatedly do the same thing to both sides of the equation until the variable is isolated on one side of the equal sign and the answer on the other.

-3a - 6 = 1 + 6a
-3a = 1 + 6a + 6
-3a - 6a = 1 + 6
-9a = 7
a = \( \frac{7}{-9} \)
a = -\(\frac{7}{9}\)

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 -21 as well and sum (Inside, Outside) to equal 4. For this problem, those two numbers are -3 and 7. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 4y - 21
y² + (-3 + 7)y + (-3 x 7)
(y - 3)(y + 7)

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.

(5a)(5ab) + (6a²)(7b)
(5 x 5)(a x a x b) + (6 x 7)(a² x b)
(25)(a¹⁺¹ x b) + (42)(a²b)
25a²b + 42a²b
67a²b

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(5 + 4)(3)
a = ½(9)(3)
a = ½(27) = \( \frac{27}{2} \)
a = 13\(\frac{1}{2}\)