The given equation is in the form ax^2 + bx + c = 0, where
a = 2
b = -12
c = 18
Those a,b,c values are plugged into the discriminant formula below
d = b^2 - 4ac
d = (-12)^2 - 4(2)(18)
d = 144 - 144
d = 0
The discriminant is zero, so there is only one real root. This root is specifically a rational number.