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)(2ab) + (2a²)(3b)
(3 x 2)(a x a x b) + (2 x 3)(a² x b)
(6)(a¹⁺¹ x b) + (6)(a²b)
6a²b + 6a²b
12a²b

When solving an equation with two variables, 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.)

A right angle measures 90 degrees and is the intersection of two perpendicular lines. In diagrams, a right angle is indicated by a small box completing a square with the perpendicular lines.

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

y² - 4y - 21 = 0
(y + 3)(y - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (y + 3) or (y - 7) must equal zero:

If (y + 3) = 0, y must equal -3
If (y - 7) = 0, y must equal 7

So the solution is that y = -3 or 7

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

r = \( \frac{d}{2} \)
r = \( \frac{4}{2} \)
r = 2
a = πr²
a = π(2²)
a = 4π