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.

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

z² - 9 = 0
(z - 3)(z + 3) = 0

For this expression to be true, the left side of the expression must equal zero. Therefore, either (z - 3) or (z + 3) must equal zero:

If (z - 3) = 0, z must equal 3
If (z + 3) = 0, z must equal -3

So the solution is that z = 3 or -3

A triangle is a three-sided polygon. It has three interior angles that add up to 180° (a + b + c = 180°). An exterior angle of a triangle is equal to the sum of the two interior angles that are opposite (d = b + c). The perimeter of a triangle is equal to the sum of the lengths of its three sides, the height of a triangle is equal to the length from the base to the opposite vertex (angle) and the area equals one-half triangle base x height: a = ½ base x height.

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.

According to the Pythagorean theorem, the hypotenuse squared is equal to the sum of the two perpendicular sides squared:

c² = a² + b²
c² = 3² + 3²
c² = 9 + 9
c² = 18
c = \( \sqrt{18} \)