Question 298733
    The distance traveled by an object moving in a straight line is given by s = t2 - 8t, where s is in feet and t is the time in seconds the object has been in motion. How long (to the nearest tenth) will it take the object to move 9 feet? 
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The problem gives you the formula:
{{{ s = t^2 - 8t}}}
Simply substitute s for 9 and solve for t:
{{{ 9 = t^2 - 8t}}}
{{{ 0 = t^2 - 8t - 9}}}
Factoring the right side:
{{{ 0 = (t+1)(t-9)}}}
t = {-1, 9}
We can toss out the negative solution leaving:
t = 9.0 secs