Final answer:
The quadratic inequality that represents the area of the garden must be below 216 is X^2 + 6X - 432 < 0.
Step-by-step explanation:
To find the quadratic inequality that shows the area of the garden must be below 216, we need to use the formula for the area of a triangle.
Since the height is 6 meters longer than its base, we can represent the base as X and the height as X + 6.
The area of the triangle is given by the formula A = (1/2) * base * height.
Substituting X for the base, the inequality becomes (1/2) * X * (X + 6) < 216.
Expanding and simplifying the inequality, we get X^2 + 6X - 432 < 0.
This is the quadratic inequality that represents the area of the garden.