If f(x)=3x^2+4x+5, what must the value of k equal so that the graph of f(x-k) will be symmetric to the y-axis?

Question

Choices:

(a) -4

(b) -4/3

(c) -2/3

(d) 2/3

(e) 4/3

Answer 1

The way I look at this is that for f(x) the x coordinate of the vertex will be at -2/3 Remember that the x coordinate is at -b/2a

So to make the graph symmetric around the Y axis I need to shift the graph (2/3) to the right so k =2/3

Answer 2

What is being asked here is for what value of k is f(x-k)=f(-x-k).

Expand the 2 expressions and set them equal...you will wind up with -6kx+4x=6kx-4x

For x not equal to 0, this means k=2/3.and for x=0 k must be equal to 0 so NO value of k works for all x.