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.

9a⁸ - 2a⁸ = 7a⁸

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 + 4)(y - 9)
(y x y) + (y x -9) + (4 x y) + (4 x -9)
y² - 9y + 4y - 36
y² - 5y - 36

A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.

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.

4y + 8 = 3 - y
4y = 3 - y - 8
4y + y = 3 - 8
5y = -5
y = \( \frac{-5}{5} \)
y = -1

The formula for circumference is circle diameter x π. Circle diameter is 2 x radius:

c = πd
c = π(2 * r)
c = π(2 * 6)
c = 12π