Question

Find the vertex of the graph of the function.

f(x) = 2x2 - 8x + 9

( 0, -1)

( -1, 0)

( 2, 1)

( 1, 2)

I don't end up with either of the answers, can you explain how you find the answer but don't give me the answer

Answer 1

You have a parabola:\[y =f(x)= ax^2+bx+c\]where \(a=2,\,b=-8,\,c=9\)

The vertex of a parabola in that form has an x coordinate of \(-\dfrac{b}{2a}\)
The y coordinate can be found by plugging in that value as \(x\)

The correct answer does appear in the list :-)

Answer 2

will -8 still be
\[\frac{ -b }{ 2a }\]

Answer 3

i meant will it still be a negative 8

Answer 4

\[-\frac{b}{2a} = -\frac{-8}{2(2)} = \frac{8}{4}=\]

Answer 5

That where i will get the 2 from but where would i get the second answer

Answer 6

That's the x-coordinate of the vertex. You find the y-coordinate by evaluating \(y=f(x)\)