Question 593595
h(t) = -9.8t^2 – 10t + 230, 
When it hits the ground, h(t) = 0, therefore
-9.8t^2 – 10t + 230 = 0 
Use the quadratic formula to find t
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
In this problem: x=t; a=-9.8; b=-10; c=230
{{{t = (-(-10) +- sqrt(-10^2-4*-9.8*230 ))/(2*-9.8) }}}
:
{{{t = (10 +- sqrt(100+9016 ))/(-19.6) }}}
I'll let you do the rather tedious math here, you should get a positive solution of about 4.36 seconds