Answer
$i, -i, \frac{\sqrt7}{6}, -\frac{\sqrt7}{6}$
Work Step by Step
$36t^4+29t^2-7 = 36t^4+36t^2 - 7t^2-7 = 36t^2(t^2+1) - 7(t^2+1)=(36t^2-7)(t^2+1)=0$
Either $36t^2-7 = 0$ giving $x= \frac{\sqrt7}{6} or -\frac{\sqrt7}{6}$
or $t^2+1=0$ giving $x=i$ or $-i$
