Y=a and y=x form a set of equations to get point A (a, a).
Y=a and y= 1/x form equations, and get point b (1/a, a).
Because AB=8/3, 1/a-a=8/3. Solve the quadratic equation of one variable and get a=-3 or a= 1/3. Because the parabola is in the third quadrant, A.
So A(-3, -3), B(- 1/3, -3)
Let y = ax 2+bx+c (a ≠ 0) (the meaning of this a is different from the last a).
Substitute point A and point B to get b= 10a/3.
The symmetry axis is -b/2a=- 10a/6a=-5/3, so the ordinate of the vertex is also -5/3.
(4ac-b 2)/4a =-5/3. Solve this equation to get c=(25a- 15)/9.
When a is substituted into y = ax 2+bx+c, -3=9a-3b+c is obtained.
Because b= 10a/3 and c=(25a- 15)/9.
So-3 = 9a-10a+(25a-15)/9. To solve this equation,
A=-3/4, so B =-5/2 and C =- 10.
So y = (-3/4) x 2+(-5/2) x- 10.
This is just a conventional solution, and there may be a simpler solution.