Answer:
y - 2 = -2/9( x - 8)
Step-by-step explanation:
hope this helps
let me know if u need more help
The quadratic equation that best represents his model of the relationship between stock value and time is given by:

The graph is given at the end of the answer.
<h3>What is the equation of a parabola given it’s vertex?</h3>
The equation of a quadratic function, of vertex (h,k), is given by:

In which a is the leading coefficient.
In this problem, the maximum value was a share value of $18 after 10 days, hence the vertex is:
(h,k) = (10,18).
Thus:

Since the initial price was of $8 per share, we have that:




Hence the equation is:

At the end of the answer, the sketch of the graph is given.
More can be learned about quadratic equations at brainly.com/question/24737967
You can conclude that it is a isosceles triangle (a triangle with 2 congruent sides)? I'm not sure though. :/