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.

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

z² + 9z + 14 = 0
(z + 2)(z + 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z + 2) or (z + 7) must equal zero:

If (z + 2) = 0, z must equal -2
If (z + 7) = 0, z must equal -7

So the solution is that z = -2 or -7

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 - 7)(y - 8)
(y x y) + (y x -8) + (-7 x y) + (-7 x -8)
y² - 8y - 7y + 56
y² - 15y + 56

A parallelogram is a quadrilateral with two sets of parallel sides. Opposite sides (a = c, b = d) and angles (red = red, blue = blue) are equal. The area of a parallelogram is base x height and the perimeter is the sum of the lengths of all sides (a + b + c + d).

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.

7a - 4a = 3a