Let f(x) = r2s2x2 + 6rstx + 9t2
Now, if we recall the identity
(a + b)2 = a2 + b2 + 2ab
Using this identity, we can write
r2s2x2 + 6rstx + 9t2 = (rsx + 3t)2
On putting f(x) = 0 , we get
(rsx + 3t)2 = 0

Thus, the zeroes of the given polynomial r2s2x2 + 6rstx + 9t2 are -3t/rs and -3t/rs.
Verification

So, the relationship between the zeroes and the coefficients is verified.