To solve this equation, 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.)

8c(c - z)
8(-5)(-5 + 9)
8(-5)(4)
(-40)(4)
-160

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

z² - 12z + 35 = 0
(z - 5)(z - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 5) or (z - 7) must equal zero:

If (z - 5) = 0, z must equal 5
If (z - 7) = 0, z must equal 7

So the solution is that z = 5 or 7

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).

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

c = πd
c = π(2 * r)
c = π(2 * 10)
c = 20π

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 -28 as well and sum (Inside, Outside) to equal 3. For this problem, those two numbers are -4 and 7. Then, plug these into a set of binomials using the square root of the First variable (y²):

y² + 3y - 28
y² + (-4 + 7)y + (-4 x 7)
(y - 4)(y + 7)