Answer:
81x^2 -27x -40 = 0
Step-by-step explanation:
When a/b is a root of the equation, one factor of the equation might be ...
(bx -a)
Hence the factored form of the equation you seek might be ...
(9x +5)(9x -8) = 0
and the standard form will be that product multiplied out:
81x^2 -27x -40 = 0