The volume of a rectangular solid is given by V = abh, where a, b, and h are the length, width, and height of the solid, respectively. We are given that the height of the rectangular solid is 20 cm, and its volume is 120 cm³. Substituting these values into the formula, we get:
120 = ab(20)
Simplifying this equation, we get:
b = 6/a
Therefore, the formula that defines b in terms of a is b = 6/a.
This formula is an indirect proportion because as the value of a increases, the value of b decreases, and vice versa. In other words, the product of a and b is constant (in this case, 120), so if one of the variables increases, the other must decrease to maintain the same product.
The domain of this function is all positive real numbers except for a = 0, since division by zero is undefined. Therefore, the domain of the function is (0, ∞).