For this case we have:
By trigonometric property we have:

Where:

Substituting:

Clearing x we have:

Thus, the equation is: 
Answer:

Here is the final answer
3 2/9
=29/9. Hope it help!
13/35 because you have to find the common denominator which would be 35 and in order to get 7 to 35 you have to multiply the whole thing by 5 making the fraction equal 15/35 and you have to multiply the other fraction by 7 making it 7/35 add the two together which would equal 22/35 so to make that 35/35 it would have to be 13/35
For the answer to the question above,
My answer in which <span>equation represents the boundary for the region where the station can be heard</span> would be multiple choice letter <span>D. (x + 6)^2 + (y + 1)^2 = 16
I hope my answer helped you solve your problem, Have a nice day!</span>