by tommywallach Sun Apr 14, 2013 11:25 pm
Hey Chavi,
The best way to find a minimum is just to test values. It'll never take long.
f(x) = x^2 + 4x - 5
We can already see that positive numbers aren't going to get us to a minimum, so let's start searching downwards.
x = 0, f(x) = 0 + 0 - 5 = -5
x = -1, f(x) = 1 - 4 - 5 = -8
x = -2, f(x) = 4 - 8 - 5 = -9
x = -3, f(x) = 9 - 12 - 5 = -8
Looks like we found the minimum! It's x = -2, f(x) = -9. Tada!
-t
P.S. This method is discussed in the book. There's no need for graphing/a graphing calculator ever, but it is definitely reasonable for them to ask for the minimum value of a function (it'll always be an integer, though, or else it would be way too hard to find).