jmc

Question

On a particular day in Salt Lake, UT, the temperature was given by -t^2 +12t+50 where t is the time in hours past noon. What is the largest t value at which the temperature was exactly 77 degrees?

Accepted Answer

We set the temperature equal to 77 degrees: align* -t^2 +12t+50&=77 t^2-12t+27&=0 (t-3)(t-9)&=0 align*We see then that the temperature is 77 degrees exactly twice: at t=3 and t=9, so our answer is 9.