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.

(3a)(5ab) - (9a²)(3b)
(3 x 5)(a x a x b) - (9 x 3)(a² x b)
(15)(a¹⁺¹ x b) - (27)(a²b)
15a²b - 27a²b
-12a²b

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 > sign and the answer on the other.

7a + 9 > \( \frac{a}{4} \)
4 x (7a + 9) > a
(4 x 7a) + (4 x 9) > a
28a + 36 > a
28a + 36 - a > 0
28a - a > -36
27a > -36
a > \( \frac{-36}{27} \)
a > -1\(\frac{1}{3}\)

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).

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

c² - 5c - 6 = 0
(c + 1)(c - 6) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (c + 1) or (c - 6) must equal zero:

If (c + 1) = 0, c must equal -1
If (c - 6) = 0, c must equal 6

So the solution is that c = -1 or 6

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.