Which form most quickly reveals the vertex?

a. f(x)= -3(x+1)(x+5)

b. f(x)= -3x^2 +12x+15

c. f(x)= -3(x-2)^2 +27

what is the vertex?

( , )

Step-by-step explanation:

A

A will give you the roots (the x intercepts) just by reading the numbers and doing a small adjustment.

x + 1 = 0

x = - 1            So one of the roots is (-1,0)

x + 5= 0

x = - 5           The other root is (-5,0)

A is not the answer.

B

I have graphed B so that you can see that A is true. See below, Even so, B is in standard form and it is not the answer.

C

The answer is C. The vertex is at 2,27

x - 2 = 0

x = 2

The maximum value is located at 27 which is just read.

That point (2,27) is plotted on the graph.