Answer:
The minimum value of f(x) is -21 and it occurs at x = 1
Step-by-step explanation:
f(x) =3x^2-6x-18
Factor out the greatest common factor out of the first two terms
f(x) =3(x^2-2x)-18
Complete the square
-2x/2 =-1 (-1)^2 = 1
Add 1 (But remember the 3 out front so we are really adding 3 so we need to subtract 3 to remain balanced)
f(x) = 3(x^2 -2x+1) -3 -18
f(x) = 3(x-1)^2 -21
This is vertex form
f(x) = a(x-h)^2 +k where (h,k) is the vertex and a is a constant
The vertex is (1,-21)
Since a > 0 this opens upward and the vertex is a minimum
The minimum value of f(x) is -21 and it occurs at x = 1
