Question 682261

"A toy rocket is launched from ground level. Its distance in feet from the ground in t seconds is given by the formula {{{s(t)=-16t^2+208t}}}

I need to know when will the rocket be 550ft from the ground?

I already plugged in 550 for s(t) but am unsure of how to proceed further.
.
That is the right approach.
{{{550=-16t^2+208t}}}
{{{0 = -16t^2+208t-550}}}
{{{0 = 16t^2-208t+550}}}
{{{0 = 8t^2-104t+275}}}
.
applying the "quadratic formula" yields:
t = {9.31, 3.69}
so, the rocket will be at 550 feet at
3.69 seconds (on the way up)
and again at
9.31 seconds (on the way down)
.
.
Details of quadratic formula follows:
*[invoke quadratic "t", 8, -104, 275 ]