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

z² - 11z + 28 = 0
(z - 4)(z - 7) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 4) or (z - 7) must equal zero:

If (z - 4) = 0, z must equal 4
If (z - 7) = 0, z must equal 7

So the solution is that z = 4 or 7

The area of a trapezoid is one-half the sum of the lengths of the parallel sides multiplied by the height:

a = ½(b + d)(h)
a = ½(2 + 8)(2)
a = ½(10)(2)
a = ½(20) = \( \frac{20}{2} \)
a = 10

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°).

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.

5a - 5a = 0a