Graph f(x) = 2x² + 8x - 1. What are axis of symmetry, vertex and y-intercept of the function

The correct answer is: -1

 
                                  

This quadratic function is in standard form, f(x)=ax²+bx+c.
For every quadratic function in standard form the axis of symmetry is given by the formula x=−b/2a.
In f(x)=2x²+8x-1, a=2, b=8, and c=-1. So, the equation for the axis of symmetry is given by
x = −(8)/2(2)
x = - 8/4
x = -2
The equation of the axis of symmetry for f(x)=2x²+8x-1 is x = -2.
The x coordinate of the vertex is the same:
h = -2
The y coordinate of the vertex is :
k = f(h)
k = (h)² + 8(h) - 1
k = 2(-2)² + 8(-2) - 1
k = 8 – 16 - 1
k = -9
Therefore, the vertex is (-2 , -9)
For finding the y- intercept we firstly rewrite the equation by substituting 0 for x.
y = 2(0)² + 8(0) - 1
y = 0 + 0 - 1
y = -1
Therefore, Axis of symmetry is x = -1
Vertex is ( -2 , -9 )
Y- intercept is -1.