If t is a real number, what is the maximum possible value of the expression -t^2 + 8t -4?
Here's a hint: Complete the square.
Due to the leading negative on the t^2 term, this is a dome shaped parabola
Maximum will occu at t = -b/2a b = 8 a = -1
use this value of 't' in the equation to find the maximum value ....