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 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 -20 as well and sum (Inside, Outside) to equal 1. For this problem, those two numbers are -4 and 5. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + y - 20
y² + (-4 + 5)y + (-4 x 5)
(y - 4)(y + 5)

To solve this equation, isolate the variable for which you are solving (b) on one side of the equation and put everything else on the other side.

-3b + 3x = -6b + 9x - 9
-3b = -6b + 9x - 9 - 3x
-3b + 6b = 9x - 9 - 3x
3b = 6x - 9
b = \( \frac{6x - 9}{3} \)
b = \( \frac{6x}{3} \) + \( \frac{-9}{3} \)
b = 2x - 3

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.

2a³ - 5a³ = -3a³

The formula for area is πr²:

a = πr²
a = π(4²)
a = 16π