Given f (x) = - x2 + 6 x -11 determine each of the following.
(a) f ( 2)
(b) f ( -10)
(c) f (t )
Solution
(a) f ( 2) = - ( 2)2 + 6(2) -11 = -3
(b) f ( -10) = - ( -10)2 + 6 ( -10) -11 = -100 - 60 -11 ) -171
Be careful while squaring negative numbers!
(c ) f (t ) = -t 2 + 6t -11
Recall that we substitute for the x's whatever is in the parenthesis on the left. Frequently this will be something other than a number. Thus, in this case we put t's into for all the x's on the left.