Potential roots have the format
factors of the constant term
-------------------------------------
factors of the initial term
Here, 7/3 is the only possible root that has a 7 in the numerator and a factor of 9 in the denominator.
Verify that 7/3 is a root using synthetic division.
One fact you can use is 4+4 or 5+3.
Given:

It's required to find cos 2θ.
We use the formula:

Substituting:

Operating:

Answer: 1/25
Misspelled 14 to the 3rd power is 2744