[tex]\sf \dashrightarrow t = 6r^2 + 12t[/tex]
[tex]\sf \dashrightarrow -6r^2 = 12t-t[/tex]
[tex]\sf \dashrightarrow -6r^2 = 11t[/tex]
[tex]\sf \dashrightarrow 6r^2 = -11t[/tex]
[tex]\sf \dashrightarrow r^2 = -\dfrac{11t}{6}[/tex]
[tex]\sf \dashrightarrow r = \pm \sqrt{-\dfrac{11t}{6} }[/tex]
[tex]\dashrightarrow \sf r=\pm i\sqrt{\dfrac{11t}{6}}[/tex]
