From the problem, we have :
[tex]6x^2-8x-8=0[/tex]The nature of the roots depends on the value of b^2 - 4ac.
If the result is greater than or equal to 0, the roots are rational.
If the result is less than 0, the roots are irrational.
From the equation, we have :
a = 6, b = -8 and c = -8
[tex]\begin{gathered} b^2-4ac=(-8)^2-4(6)(-8) \\ \Rightarrow64+192=256 \end{gathered}[/tex]Since the result is greater than 0, the roots are rational.