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.

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.

2a⁴ - 3a⁴ = -1a⁴

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 - 9z = -5b - 3z + 6
3b = -5b - 3z + 6 + 9z
3b + 5b = -3z + 6 + 9z
8b = 6z + 6
b = \( \frac{6z + 6}{8} \)
b = \( \frac{6z}{8} \) + \( \frac{6}{8} \)
b = \(\frac{3}{4}\)z + \(\frac{3}{4}\)

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.)