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

a² - 10a + 16 = 0
(a - 2)(a - 8) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (a - 2) or (a - 8) must equal zero:

If (a - 2) = 0, a must equal 2
If (a - 8) = 0, a must equal 8

So the solution is that a = 2 or 8

The formula for area is πr²:

a = πr²
a = π(2²)
a = 4π

Parallel lines are lines that share the same slope (steepness) and therefore never intersect. A transversal occurs when a set of parallel lines are crossed by another line. All of the angles formed by a transversal are called interior angles and angles in the same position on different parallel lines equal each other (a° = w°, b° = x°, c° = z°, d° = y°) and are called corresponding angles. Alternate interior angles are equal (a° = z°, b° = y°, c° = w°, d° = x°) and all acute angles (a° = c° = w° = z°) and all obtuse angles (b° = d° = x° = y°) equal each other. Same-side interior angles are supplementary and add up to 180° (e.g. a° + d° = 180°, d° + c° = 180°).

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.

5a x 8b = (5 x 8) (a x b) = 40ab

A quadrilateral is a shape with four sides. The perimeter of a quadrilateral is the sum of the lengths of its four sides.