Is it possible to solve this?

Uh, I think you put the wrong number in the denominator. You put what would be C instead of A.

Wouldn't it actually be... (Sorry it's so messy, I don't really understand how to use mathurl)..

Code:

(-42x +/- sqrt((42x)^2-4*9*(13-49x^2))) / (2 * 9)
(-42x +/- sqrt(1764x^2-36(13-49x^2))) / 18
(-42x +/- sqrt(1764x^2-468+1764x^2)) / 18
(-42x +/- sqrt(2(1764x^2)-468)) / 18
(-42x +/- sqrt(3528x^2-468)) / 18

Not sure if I can go further.