Question 246717
We are going to use  a little trick to solve this.
Substitute u for t^2
That gives us
u^2-11+18=0
we can solve with the factoring, quadratic formula or complete the square
factoring is the easiest
(u-2)(-9)=0
u=2
u=9
but u=x^2 so
+\- means plus or minus
+\-t=sqrt(u)
so we have four solutions
t=+\-sqrt(2)
t=+\-3
see below to use the quadratic formula
*[invoke quadratic "x", 1, -11,18 ]