Question

What are the coordinates of the vertex for f(x) = 2x2 + 4x + 9?
a. (−2, 4)

b. (−1, 7)

c. (1, 15)

d. (2, 9)

Answer 1

vertex when the slope = 0
can you differentiate the function?

Answer 2

4x + 4 = 0
solve for x x = -1
what is f(-1)? this is the y value
so choice b

Answer 3

another approach
x = -b/2a
= -4/2*2 = -4/4 = -1
y = f(-1) = 2(-1)^2 + 4(-1) + 9 = 2 - 4 + 9 =11-4 = 7 choice b