After t seconds the height is f(t)=-16t2+78t+6.
When f(t)=0 the poodle will be at ground level, so:
-16t2+78t+6=0,
8t2-39t-3=0 (dividing by -2),
Using the quadratic formula, t=(39+√(392+96))/16=(39+√1617)/16=4.95 seconds approx.
So it will take about 4.95 seconds to reach the ground.