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.

Perimeter is equal to the sum of the four sides:

p = a + b + c + d
p = 3 + 9 + 2 + 2
p = 16

The first step to solve a quadratic expression that's not set to zero is to solve the equation so that it is set to zero:

z² - 4z + 10 = 5z - 4
z² - 4z + 10 + 4 = 5z
z² - 4z - 5z + 14 = 0
z² - 9z + 14 = 0

Next, 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 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.

(2a)(5ab) - (3a²)(2b)
(2 x 5)(a x a x b) - (3 x 2)(a² x b)
(10)(a¹⁺¹ x b) - (6)(a²b)
10a²b - 6a²b
4a²b

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 + 2)(y + 2)
(y x y) + (y x 2) + (2 x y) + (2 x 2)
y² + 2y + 2y + 4
y² + 4y + 4