of all numbers whose difference is 18, find the two that have the minimum product. what are the two numbers…

of all numbers whose difference is 18, find the two that have the minimum product. what are the two numbers? (use a comma to separate answers as needed.)
Answer
Explanation:
Step1: Set up variables
Let the two numbers be (x) and (y). Assume (x>y), so (x - y=18), then (x=y + 18). The product (P=xy=y(y + 18)=y^{2}+18y).
Step2: Find the minimum of the quadratic function
For a quadratic function (P(y)=ay^{2}+by + c) ((a = 1), (b = 18), (c = 0)), the vertex of the parabola (y=-\frac{b}{2a}). Substitute (a = 1) and (b = 18) into the formula (y=-\frac{18}{2\times1}=-9).
Step3: Find the other number
Since (x=y + 18), when (y=-9), (x=-9 + 18=9).
Answer:
(9,-9)